avira or avg :P
both of these are free to personal usage
both of these can be run at linux (if you are sharing files between windows and linux yes you need to have av on linux :P)
im using on stationary pc avira and on laptop avg cant tell wich one is best :P they are fast, free to use, and very effective few friend used to have other av sh1t (avast, symantec, kaspersky etc) but after they get some trojans or other suvenirs into system they tryed one of these two and clean mess on their hhd's