Well, I used to use WindowBlinds, but agreed, it's a memory hog. Use TuneUp Utilities 2006. Not only is it a great program for getting rid of extra junk on your system/overall cleanup, but it has a style program attached where you can change your visual style, boot screen, icons, etc. Try it out.
Whoops, forgot to add StyleXP. That's another program, but not as good as TuneUp.