this should be in "Operating Systems and Software"
anyway, press ctrl+alt+del and close all programs except for the ones neccesary for Windows to run
so if it's anything up to Windows ME, close all but explorer
if it's Windows 2000 or above, close everything except for 4 svchost's, explorer, services, winlogon, lsass, smss, csrss and spoolsv
then try and uninstall
if that fails, reboot to safe mode (press f8 before the windows loading screen comes up and select safe mode) then when windows loads try and uninstall it there