What is the best Free Adware/SpyWare remover and blocker& do they work on viruses too if not which is the?

best free one for that Also what are the Most essential programs to have in the Add/Remove program section like what are the ones i should not under any circumstances delete in order to have the computer run well Thanks in advance

I use AVG anti-spyware and AVG anti-virus. Free downloads at grisoft.com They both work great for me.

advanced virus remover