virus

My name is DON
OS win 2000
I am sure I have the Isass.exe virus on
my machine, I have tried several methods
to remove this virus off the machine still
my machine suddenly popup us a message
stating that the machine will shut down
How can I remove this virus off my machine?
Does win2000 have restore points??
or allow you to restore back to an earlier time.

Please help

Thanks

DON..