I use XP as well, and I haven't had any problems using right click > Rename to add the designer's name to the front end of the file name, for any kind of file. Then I sort kits by subject, and when I have enough collected in a category, I burn to a disc and delete the files from my hard drive. If you can't rename the actual file, try putting everything in a kit into a folder with the designer's name and the kit name. If you have a preview thumbnail for the kit, put this file at the bottom of the list inside the folder and that should be one of the images that shows on the outside of the folder. This way you can group by kit, but you'll still be able to see that certain background color without opening every folder. If the kit doesn't come with a preview, copy the sample from the download page, or make your own sample page and reduce to 300x300 pixels, big enough to print clearly on a contact sheet, without taking up much file space.

HTH,
KayLynn