There is a post above with a suggestion for that. Basically just get them randomly generated. They are unlikely to clash, but there are tools to check for clashes.

Yeah, I found that post. That was what my question was about. I was wondering how to generate them. I guess a cres filename looks like this: C66F7634-475A-4E3B-9B66-4FEA16DF9717
So then my GUID would be 0xC66F7634 right?

Oh... I'm not sure how the CRES name is made, and which bit is more likely to be unique.

Well that comes from this site: http://createguid.com/
I thought for random generating a new GUID I would go to SimPE going to Tools -> Object tools -> hash generator and then one of the 3 radio buttons, but I don't know which one (I guess the first, but I have to be sure of course) and then there are still 2 numbers that look like a GUID.
What do I have to use?

Where would I find a tool that can help with preventing GUIDs from clashing?

SimPE already has the best tool for creating these values.

Go to Tools -> Object Tools -> Hash Generator...

If you are creating a 32-bit value, what is called a GUID is posts earlier, something like 0x3552B33D, you would use the CRC-32 generator. Leave the seed and polynomial as the default value, and enter a descriptive name in the String field. If you use your creator name as part of the string, it will ensure that your number is unique and will not class with other creator's numbers. I would suggest something like this for the string: "granthes_MyChair_47" so that it contains your creator name, your objects name and possibly a number to ensure that it doesn't clash with your own creations.

If you are creating a 128-bit value, what is called a CRES filename, 479e2600-8696-4654-bac8-072c02f0881b, use the GUID generator. These numbers are *very likely* to be unique, and there are well over 1 trillion available, so clashes will be unlikely.

For more information on GUIDs, please see this link

So we don't need the CRC 24 one.
I used CRC 32:
This is the name of the package: meshbookswdvuitgespeeldrequested-liente-20110107
Seed: 0xffffffff
Poly: 0x04C11DB7
Hash value: 0xBC5A46D4

So I use this as GUID: 0xBC5A46D4
And do I have to add 0xffffffff and 0x04C11DB7 somewhere? Like the Orig. GUID and Fallback GUID (normally I don't do that). Or do I just use 0xBC5A46D4 as GUID?

Don't touch the Orig and Fallback GUIDs. Just the GUID of the current object. On a multi-tile object you need one new one for every OBJD.

Ok, so I'll just use 0xBC5A46D4 for this object then.
Thank you so much for this. Now I'm gone creating what I wanted to create this afternoon.
Again thank you so much for solving this problem (for me).

Edit:
Just out of curriosity: What's the difference between CRC 24 and CRC 32 (I use CRC 32 as suggested)?

A somewhat technical answer:

CRC is an acronym for Cyclic Redundancy Check. Originally it was used to detect when data transmitted over a modem became corrupted. See this wiki article if you want more details.

The number just specifies how big the value is... It represents the number of bits in the CRC. Therefore CRC-32 is a 32 bit value, and has 8 Hex digits to display. CRC-24 is a 24 bit value and only needs 6 Hex digits to display.

I don't mod for TS2, so I don't know where CRC-24 is used.

I'm seeing a lot of very confusing bits of information here about GUIDs, so I'm just going to point out a few quick, important things:

This issue only applies if you are making new TS2 object meshes!

If you're modding TS3, you can ignore the GUID issue. This is for TS2 GUIDs only.

If you are creating recolours, body parts, global hacks, or anything at all other than new custom object meshes, then you can ignore the GUID issue. It does not apply to you

An OBJD GUID is a different thing to a typical GUID.

The GUIDs generated by sites like http://createguid.com/ or the Hash Generator will not give you a unique GUID for TS2 OBJDs! Those GUIDs are designed for a different purpose, which is why we have a TS2 GUID database in the first place.

HOW TO GET A NEW GUID, IF YOU ACTUALLY NEED ONE
If you have ever registered a GUID for an object, then you probably already have a range assigned to you. Check through your last few objects, and see if the first few digits of the GUID are always the same. If they are, then go to your most recently registered object, and copy out that GUID number. Now add 1 to it (remember that it is hex, not decimal, so 9 + 1 = A, and A + 1 = B, and F + 1 = 10). That will be your new GUID. You can continue to do this until the last two digits of your GUID become FF. Just take a note of which numbers you used, and once the database comes back online then you can register them as used.
THIS SHOULD SOLVE THE GUID PROBLEM TEMPORARILY FOR MOST USERS

If you have not yet got a GUID block assigned to you, or your current block is full and you need to get a new one, then you will need to get a random number until the GUID database comes back. Here's how to get one:
Go to www.random.org
Have it generate you a random number between 7733247 and 1879048192.
Turn that number into hex. You can use this handy tool to do that: http://easycalculation.com/decimal-converter.php
This will be your GUID.

Using random numbers, there is no foolproof way to ensure that you won't clash with another object, but in the absence of a GUID registry it's a pretty good chance. It is at least as safe, if not more so, than using the online GUID tools.

This issue is not related to the "fix TGI" functionality in SimPE
The existing "Fix TGI" tool, which renumbers the type/group/instance values for the CRES/GMND/GMDC etc, is not affected by this issue. You can continue using these as usual.

About ambertation
Ambertation is quaxi's site, and no one should be 'taking over' the guid database until we can ascertain what has actually gone wrong. If it does need to be moved, then I would suggest that Quaxi and the the Joneses would be best people to decide on a new home, as they are the primary contacts regarding SimPE. I'm sure everyone's offer of hosting is appreciated, but at this point it is premature and just confusing the issue. It would be best to refrain from making any more suggestions about it until the actual problem has been identified and a course of action decided upon.

This is brilliant!

I only have to use my calculator in windows, put it into advanced mod and click the HEX.
Within my range I have the same 6 numbers in the beginning and only the last 2 are changing.
Last GUID I had was ending with AA. If I type the AA on my calculator and +1, I get AB.

Great!!! Thank you ever so much Echo

Just remember that when the database comes back up again, you'll need to mark those extra numbers you calculated as used. That way, the next time you try and register through the website it won't send you that number again.

Thanks, Echo, this is very useful.

Just a few remarks:

I guess it has to be the last two digits become FF. (16 x 16 = 256).
The first six digits belong to the GUID-block, I think.

I don´t actually understand why to create a random number between 0 and 134217727. As it was posted on the page before, Tinkle´s last GUID was 0x007055FF. Wouldn´t it make sense to generate a random number which starts definitely above this value to avoid duplicates? If you start at, let´s say, 0x0075FFFF, this would mean a decimal start value of 7733247, and the maximum GUID could be 0xFFFFFFFF which means a decimal value of 4294967295.
So wouldn´t it be better to generate a random number between 7733247 and 4294967295?

julsfels, quite right. I actually fixed the two/three digits thing about three minutes before you posted. I'll update the lower bound for the random number generation now, as I hadn't thought of that. I have a vague memory somewhere along the line of 0x7FFFFFFF being the highest allowable GUID though (is it a signed integer, perhaps?)... I might be getting my games mixed up though, that happens quite often!

I'd avoid anything above 0x7F000000, since TS2 uses those itself.

Ah!
But do you mean 0x7FFFFFFF (8 digits) or 0x07FFFFFF (7 digits).
Because 134217727 is 0x07FFFFFF, and 0x7FFFFFFF is 2147483647 in decimal, which would be a wider range.

EDIT: if TS2 uses GUIDs above 0x7F000000, maybe we should stop at 0x70000000 or so. Which is 1879048192 in decimal.
Gosh, this is difficult.
Hope the GUID-Database is back soon.

Agreed, and done.

I think I should be ok during this time of need, I have about 200 numbers left in my range(just past 50 in the first 2 digits), which should last me a few months, I just have to make sure that I write down the name of the objects, so I can register them whenever is possible

I also hope that something can be worked out whenever the knowledge of the issue does surface, I couldn't tell you how much I relied on that site for getting GUIDs, and I'm sure many others would probably say the same thing

I downloaded (from sourceforge) and do my very first attempt with the simPE. Just only a few second trying (I have a tutorial open on my browser) It says that the object workshop (or something similar) is obsolete. Then I can ever open the program again.. What should I do?

Also if you get back a random number starting with the first two digits covered by the database of issued numbers, best to throw it back and get another. Didn't they all start 00 so far?

I just heard back from Quaxi:

"The site is down (probably until monday) because the SimPE-KnowledgeBase was compromised during my vacation. But it will be back "

So, no panic. I will also take this opportunity to let him know about the ongoing problems people are having getting new database accounts and blocks.

So if I just wait until Monday I can get a GUID like I always did? Thank heaven :D
I only created one object using the hash generator CRC 32. I guess I'd better don't use it anymore and give it another GUID on Monday.

Thank goodness for that, thanks for the information, Inge!

Thanks Inge, good news!
And to enable the possibility to register would be really fine. I have two or three questions each month from people who start meshing for the Sims 2 and don´t know what to do. Seems to me, that creating new stuff for Sims 2 is far away from beeing dead.