Which one do you have? Windows 2000 or Windows ME? There is actually a huge difference. Windows 2000 and XP can download something like windows blinds and install theme packs. http://www.stardock.com/products/windowblinds/downloads.asp
However, you will need to locate a very old version to install on Windows 2000. As for Windows 95,98, and ME... Windows Blinds won't work and is not compatible with the code.