Cant install programs on Win2k!! Try to install something, nothing happens!!

[bigronstud266]

All of a sudden I cant install programs on win2k SP3! When I try to install a program(any program) it starts up like it is going to install and then nothing else happens. The computer doesnt freeze or nothing, it just stops installing whatever it is Im trying to install.
Actually this is happening on another persons computer who has a ton of things running. Does anybody know what are the minimal programs that should be running in windows so I can close all the unnecessary ones using task manager?
Thanks for the help,
Bigron

[jeresimo]

Try doing this it might help:

Start a command session by going to Start, Run and typing :
cmd

Enter each of the following commands (the system might prompt you to enter the installation media during this process):
sfc /purgecache
sfc /scannow

Restart the computer