You cant go far wrong with these, and there all free.

AVG Anti-Virus Free Edition 7.5

http://free.grisoft.com/filedir/inst/avg75free_484a1103.exe

AVG Anti-Spyware Free Edition 7.5

http://free.grisoft.com/filedir/inst/avgas-setup-7.5.1.43.exe

AVG Anti-Rootkit Free

http://free.grisoft.com/filedir/beta/avgarkt/avgarkt-setup-1.1.0.42.exe