If you are getting user32.dll or shell32.dll errors while opening
specific application or file, means that these files have been
tampered or modified. These modifications can in terms of Desktop
Replacement or Interface Theme Software, it is done by you or is can
be pre build (modified) in your os. In this case try uninstalling these software
(which is causing problem or error) properly and see if error stops.
If error user32.dll or shell32.dll still occurs than try to repair
your windows files from windows cd recovery mode while booting off
through windows XP CD, or just re install new Windows XP version and
through different CD.