Patches fail to install, PC Slow

Howdy,

I am working with a Windows 2000 professional machine, and upto now the computer has worked fine, but today it wouldn’t shutdown, nor would it install a service pack or any of the patches that microsoft have on there site.

When I tried to install the patches the whole system slowed down, making it very hard to navigate around the system, I have a firewall and antivirus already so I am ruling out the possibility of being infected with a virus.

Whats wrong with this PC?