Just got done customizing my XP theme. I felt a bit out-of-date for still having XP so I went and made a custom theme. It's a pure .msstyles theme; that is, it imports just fine into XP and doesn't need a crappy program (ala WindowBlinds).
I run a dual-monitor setup nowadays, but I cut the second monitor out of the pic as it really wasn't needed. It was just a second wallpaper.
My only lament is that my desktop shows that a) I need to upgrade to a widescreen 1920x1080 monitor instead of my old 5:4 1280x1024 resolution and b) I need to upgrade my OS from Windows XP Professional to Windows 7.