I believe that the main UI font for Windows XP is Tahoma, but if you're building UI, you should use MS Shell Dlg2 (there may be a space before the 2) since that's a virtual font that will be changed ...

I saw a post from 2004 asking for the taskbar font from windows 2000 with no clear answer, and via my own testing, i have decerned that it is Tahoma Bold size 11 full hinting just incase somebody with ...