Ok, guys, I work on PCs all the time, and fix them, install software, build new systems and such.
The ONLY antivirus and firewall and spyware programs out there that actually works, are TREND MICRO.
If you want the 2nd best, go with these from http://www.download.com.
1. AVG FREE Antivirus, run in Basic Protection installation. Works perfect, catches trojans that Norton and McCaffee dont. Runs Continuously, cannot be disabled once installed. You never need to disable ANY antivirus software, regardless of what your program states. Ever.
2. ZoneAlarm Free Firewall – my hacker friends cant get through it in 6 hrs. I can get throu McCaffee and Norton in 15 mins. Runs Continuously, if its not, start it manually. Keep it up folks. It will save your PC's life, and your personal info.
3. AdAware AE – It's free, just dont go with the full suite. This is only needed about once every 3 months or so. Keep it uninstalled till you need to run it.
If you use the FREE programs above, Achat will never have a problem. DO NOT USE ANYTHING ELSE, or it will block Achat, corrupt your system, and install Viruses.
Any other PC Cleanup or Tune UP software is a JOKE, and does nothing for you. Trust me. I stopped using them about 7 years ago.
Also, for those of you using AIM or AOL ANYTHING, PLEASE STOP! AOL is a VIRUS.