1. Antivirus: Choose one - Avira, Avast, or PC Tools Antivirus. thir free
2. Antispyware: Choose one - Malwarebytes or Spyware Doctor.
3. Firewall: Zone Alarm. Some experts like the PC Tools Free Firewall. This is the one I am currently using and it does a good job.
4. Secure web browser: Explorer 8 and/or Firefox.
5.Anti-hack tool: SnoopFree Privacy Sheild Optional: Keyscrambler for Firefox, and Keepass.
6. Fraud and phishing filter: recommend that you use both WOT (Web of Trust) and Site Advisor.
7. Sand Box: This is for for added safety, virus protection, etc. recommend Sandboxie. I don't recommend this for an older computer, it slows them down.
8. Tune Up: Many people like the idea of a tune up utility that keeps the computer running like "brand new". The one I use and recommend is Advanced System Care. It works great and it is very easy to use.