Stumped. Need help please.

I got my machine back from the service center when I noticed it has missing dlls. Can't even launch Chrome. Restored to original settings but I'm worried my machine may have a virus so I tried to run DBAN. I'm getting a "non-fatal error... due to bad sectors..."

Ran CHKDSK and it came back with zero bad sectors.

I'm stumped.

Any tips on how I can get this wiped so I can start over? Been meaning to switch to a Linux system and dual-boot with the win7 OEM.

TIA!