I downloaded your black & gold theme, extracted it & everything looks file on XP.

Maybe it's a Vista issue. I don't know, I don't use Vista. Have you used Google to see whether anybody else has had the same kind of problem? Try the links below & see if anything helps.
.zip files will not extract in Vista Business OS

ITsVISTA Tip 16: Using Vista to Zip and UnZip Files and Folders | ITsVISTA

Zip extract is empty directory structure - Vista File Management