KEYS "e,d,c and 3" of LAptop (Hp nx7300) not working?

i have HP nx7300 laptop, and from few days my keys, ie.,’3′, ‘e’ d’, ‘c’ are not working. Kindly help me, it may be passible tht my laptop id virus infected as i was not using any antivirus for some time. i just started using avast which had detected Win:32 sality virus in my laptop, Kindly guide me whether it is a problem related to virus, BIOS or hardware.