|Not sure I completely understand what's going on here. You're running XP which has no built-in sidebar so the one you're looking at must have been installed by some program.|
I find it odd you never noticed it before. Have you installed any windows blind type of programs that make the XP desktop look like Vista or Windows7?
Any names, icons, etc. on that sidebar? Or, is it blank?
Have you tried msconfig to see what's loading at startup?