What are the best ways to optimize my PC performance?

I understand pretty much the basic PC optimization techniques. Defrag, Spybot, Adaware, anti-virus, deleting cookies etc. However, I have noticed that my PC has been running slower and slower recently. Programs take a long time to load/shut down, internet pages load slower, etc. I havent added any major programs recently. I am afraid I might have picked up some really sneaky malware, viruses or rootkits. What are some really good techniques to optimize my PC for a person with an average PC IQ?

p.s. antivirus is AVG free addition, firewall is standard windows xp.

What are the best ways to optimize my PC performance?liveupdate

As a computer gets older it suffers from memory loss.This really slows down your speed the older the computer gets.Look in your task bar and see what programs are running on start up.Conflicting script will cause your computer to run slow too.

What are the best ways to optimize my PC performance?nortin

I would stick with AVG. I would dump Windows firewall and use one listed here http://wiki.castlecops.com/Roll_your_own...

If you think you still have malware follow the procedures here http://wiki.castlecops.com/Malware_Remov...

If you have had your computer a long time it will build up a lot of crap and you need to clean it out. These two sites tell you how to manually clean out your computer http://www.personal-computer-tutor.com/d... and http://www.bold-fortune.com/forums/index... The latter one is pretty aggressive and you should very careful about some of the recommendations. I would first recommend that you use CCleaner and ATF-Cleaner which are listed on the Malware and Prevention Overview listed above. Here is another site for manually cleaning your computer http://www.optimizingpc.com/optimize/del...