I want to install a Mac theme in XP. I've tried several transformation packs without success. Any advice on how I can do that or recommendations for good Mac or Mac-like themes?
I actually think it's not even possible get an OS X-like Windows XP theme without using transformation packs.
Windows XP has the ability to use “visual styles” that use a *.msstyles file on your hard drive. Unfortunately, Microsoft didn’t set up Windows XP to allow others to create them. The code name for the “Windows XP style” was "Luna" when XP was developed. If you look in your “C:\WINDOWS\Resources\Themes\Luna” folder, you will find a file called "Luna.msstyles". This is the "skin" that is known as the "Windows XP style".
I don't think the *.msstyles file alone can give you everything you want. I would resort to a transformation pack that has been tested by a more renowned website or that can be easily restored. Here are some guides you could follow to get some nice results:
Check out this SU thread. It's not perfect, but it's on point for changing XP look and feel to Mac (as much as possible, I guess :)
CrystalXP.Net has many "Visual Styles" for XP.