Everyone has their favourite programs, here's what I use:

Firewall: Comodo Firewall Pro The free one, not the 'Plus' version that you pay for.
AV: Avira AntiVir Personal The free one, not the 'Premium' paid version.
Malware prevention: SpywareBlaster (free)
Malware removal: Malwarebytes The free version.
And sometimes: Spybot S & D (free)

There are other freeware programs which a lot of people use...
Firewall
ZoneAlarm Firewall

AV
avast! antivirus Home Edition
AVG Antivirus Free Edition

Malware
a-squared Free
SUPERAntiSpyware
Ad-Aware Free 2008

Watch your search results & if anything looks weird (eg no info showing when you hover your cursor over the file, or just something like 'track 1' showing) then leave the file alone. If a file's less than 2000 KB - leave it alone. If a file has an extension type, in LW's 'Type' column that doesn't match what you're looking for (eg if you're looking for a music file but the search result shows as .exe or .zip) - leave it alone. Any file that has a description of .mp3.exe is a nasty.

Other links to help with crap appearing in search results:
Fake files showing up in search results

How to find music (tips for video also)

How to use Bitzi

You could also use this hostiles list & see whether that cuts down on spam: The TechNutopia Fullsize Hostiles List for BearShare and LimeWire