Scanning a hard drive for viruses

My girlfriend's computer is quite infected with viruses and spyware to the point where it's a huge hassle to do virus scans on her computer. Her 256 mbs of ram doesn't help either. I'm planning on taking her hard drive out and installing it in my computer as a slave to remove all the viruses. Does this put my computer at risk? Is there some sort I program I can download that would protect me from any viruses on her hard drive or is the whole idea not too bright in the first place?

I'm running Microsoft Antispyware and Avast Antivirus. Both are updated and I have Ad-Aware installed as well. Thanks for any help.

 

That is the best thing you could do. I don't see any reason why you would get a virus if you've got the anti virus you mentioned.