External User

I recently installed windows xp professional. The problem I am having is that
when I try to instal anything of a disk windows tells me that it can not run
windows installer because it iether I am running in safemode(Which I am not)
or that the installer was installed improperly. But I can install programs of
the internet when I download them. If anyone had any suggestions it would be
appreciated. Thank you to everyone for your help.
--
manny