For an anti-virus program, I install Microsoft Security Essentials. I used to recommend AVG free but have switched to Security Essentials because it works well and doesn't bug you to upgrade. The advantage of free even to those for whom money isn't an issue, is that it will never expire. If an anti-virus program expires and no longer updates it's as good as not having one at all.

If a computer is infected with spyware then I find Malware Bytes very good at removing spyware.

And Microsoft has a free Security Scanner.

I created a bootable USB flash drive using Xboot with several virus rescue scanners including the one provided by AVG.