I'm pretty paranoid when it comes to computer security, and overall computer efficiency. I hate doing registry crawling to eliminate any would be rogue programs or bloatware.
Anyway this is what I use, all FREE programs btw. Starting with prevention.
Use Firefox, I'm pretty sure most of you guys already use it.
http://www.mozilla.com/en-US/firefox/firefox.html
Along with Firefox install these plugins into the browser
Adblock Plus - blocks ads
https://addons.mozilla.org/en-US/firefox/addon/1865
NoScript - blocks all scripting
https://addons.mozilla.org/en-US/firefox/addon/722
With those two combine most stuff won't infect you via drive by
Also add this program for further prevention
SpywareBlaster - adds known bad sites to your restricted list.
http://www.filehippo.com/download_spywareblaster/
For those you guys who hate bloatware usually bundled with commercial software try these
QuickTime Alternative - Bare minimum plugins for the browser
http://www.filehippo.com/download_quicktime_alternative/
Real Alternate - Bare minimum plugins for the browser
http://www.filehippo.com/download_real_alternative/
System Security
Anti-virus:
AVG Free - never had much of problem with this program, catches those sneaky flash drive viruses before they can infect
http://www.filehippo.com/download_avg_antivirus/
Anti-Spyware:
Lavasoft Ad-Aware Free (with real time not installed, also disable all automatic updates to save resources!!!) I use this as a second opinion since AVG is suppose to already have an anti-spyware component.
http://www.filehippo.com/download_ad-aware/
Firewall:
Online Armor Free - easy to use, preformed pretty well on leak tests
http://www.tallemu.com/free-firewall-protection-software.html
(not sure if they still have that annoying banner on start up, i still have v2.0 but if they do you can disable it by adding a Banner.dat file into the tallemu folder)
Both AVG and Online Armor has a residence that continually monitors the system, and they do a pretty good job at it, i don't think it is necessary to use the Ad-Adware residence.
Other:
For AIM users to remove those annoying talking ads use
http://www.aimadhack.net/
For those who just like low resource consuming software use:
(I personally think anything microsoft has to offer uses too much system resources)
Music
Foobar2000 - plays pretty much every music file type in existence, can convert CD into FLAC, FLACs into MP3 etc...
http://www.filehippo.com/download_foobar2000/
Video
K-lite codec - plays pretty much any video file, use the Media Player Classic, bundled with the pack instead of that windows media thing.
http://www.filehippo.com/download_klite_codec_pack/
Maintenance:
CClean - removes junk that builds up on your system
http://www.filehippo.com/download_ccleaner/
Overall I have had pretty good success with this set up, haven't had a huge virus or malware outbreak yet. Except for thoses that likes to jump systems from flash drives. Which both the firewall and anti virus was able to catch and neutralize before it caused damage.
Also as far as system resources goes I average 45 process at start up with a commit charge of around 350M/3939M