Take it back and ask them to correct the new issue.
To figure out if it's a virus, try out of those Live CDs. I use the Ubuntu one since no install or learning of Linux is required.
After changing chip on motherboard my comp run's okey. Before that it just cant start or if I could start it, then will surely goes off not before long.
BUT after that something happen, the keypad shows something on. It sometime ok and sometime not ok. Sometime I got to push 3 or 4 time to type a single character. At another moment it seems that particular key works as normal as nothing wrong.
It is something related to virus thread or else? And how to resolve it.