Sorry, mate, but this is one of the problems that most people have when trying to use Theme Builder 3.0 on Windows Vista or 7, because it has been programmed to run correctly only on XP…
Anyway, as I explained to many others, you could try to do this:
1) First of all, you need to be sure you have Theme Builder 2.5 "Full Install" and 3.0 "Upgrade Only" versions installed on your computer. Then, be sure you also have the latest version of .NET Framework (I think that 3.5 or even 4.0 is available)
2) Now go to "lili-chan.com" site and register, then go to "Support" ==> "Official Lili-Chan Theme Builder Discussion & Support" ==> "Theme Builder v3.0 Bug Reports".
Now go to PAGE 7: in the 2nd post (by SBCroix) there's an attachment which contains the "Beta 4.0 files" for Theme Builder. Download it and READ CAREFULLY the post before using those files.
Basically, you need to replace your "3.0 files" with "4.0 Beta" ones, as explained in the post I told you to read (but remember that even so, it's not 100% sure Theme Builder will work properly…)
Good luck, bro!