My friend's XP computer is sick. I don't think it's malware (have run full scan with malwarebytes).
Windows updates fail with "msiexec has encountered a problem and needs to close". Other app updates also fail. As does installation of new software with "such and such has encountered a problem and needs to close".
At present my friend can't find his original Windows disk (perhaps a "repair" could work?).
I have tried rolling back to his earliest system restore - but that didn't do it (he only goes back about 3 months with restore).