I've searched, but haven't found out how to rename the file. I learned how to make new icons, which is uber cool.......but I can't find where to rename it so I can find it easily, instead of all those letters and numbers.

Could someone explain how to do that in SimPE for me?

**also, after I replaced the icon, I couldn't find where to commit. So I just saved. Can you tell me where to commit, or is just saving it ok. I can easily see the commit button when I recolor objects, but couldn't find it when I was working with the collection icon.

use the collection creater. you can get it in sim tools here.

Are you talking about the filename of the collection package, or about the name that appears in the catalog when you select the collection?
If the first, you can rename the filename like any other Windows file, and the game won't have any problems in using the renamed collection; if the second, you can open the package in SimPE and edit the (only) Text List in it: you can even set a different text for any language, if you like.

Thank you Numenor!!!! Yes, I meant the file name. I was going to change it by right clicking, and renaming...(that's what you mean right?) But I was afraid it couldn't possibly be that simple. Thank you!

use the collection creator it's easier.

The collection creator is very useful and easy to use (though renaming a package name is easier...). But the main problem of the CC is that it does not manage icons other than in BMP forma, while the most used formats for the icons is TGA and PNG, that allow transparency. Loading and saving (with a different name) a collection forces you to discard the existing TGA/PNG icon.

so it's not hard to convert any image to a bmp file.

Of course not but you lose the transparency. And anyway, wouldn't be just too a long process to open the collection, extract the image, convert it and then re-save the collection with the BMP, just to rename a package?
Please don't think I don't like the Collection Maker: on the contrary, I'm quite fond of it and I use it regularly; but when the collection is created, I always make the final "adjustments" with SimPE, just because I'm very anal for details...
You know, even when I export a lot, I often replace the thumbnails with my own, because I don't like the ones automatically included (the lot is always very small and barely visible...) :D

if you make the background the same blue as the other icons from the game you dont need transperency.

lol, true but that still results in a redo of the thumbnail as Numenor just stated.

what do you mean a re-do of the thunmbnail? just replace the icon image with your own image

I mean just as Numenor stated :" wouldn't be just too a long process to open the collection, extract the image, convert it and then re-save the collection with the BMP, just to rename a package?"

Collection file modding related threads:

Changing Icons For Existing Collections
http://www.modthesims2.com/showthread.php?t=123906

Collection Files?
http://www.modthesims2.com/showthread.php?t=213105

collection icon?
http://www.modthesims2.com/showthread.php?t=186283

Comunity Objects
http://www.modthesims2.com/showthread.php?t=57823

Custom Collections Icons...
http://www.modthesims2.com/showthread.php?t=96184

How to create custom Collection Folder Icon?
http://www.modthesims2.com/showthread.php?t=241536

How do I make custom "collection-icons"?
http://www.modthesims2.com/showthread.php?t=170301

Renaming collection files with SimPE http://www.modthesims2.com/showthread.php?t=179754

I am SO lost. I have downloaded SimPE, Sims Collection Creator and Sims2 Clean Pack installer. All I want to do is SEE the files and put then into a collection. The sims collection creator will not take some of the files as they dont have a GUID. I am lost. Please help.

Files with no GUID are likely to be recolors. Putting the original mesh into a collection will put the all of the recolors of that mesh in as well.