Hello and Welcome to FPCH Aldin. :)
CMOS checksum bad means that the contents of the configurable CMOS section of BIOS doesn't agree with the stored checksum (derived by a mathematical formula from the contents the CMOS should have).
In other words, the contents of that section of memory is not what you stored there and needs to be fixed. The reasons can be many, ranging from a virus to a hardware fault.
As you rightly said, that you were infected by a virus and since then, the PC failed to boot, I think it is also the reason behind your "dead" computer. In this case, I would suggest you wait till our Malware experts come online and review your case. Thank you for your patience and co-operation. :)
-- Goku