Resetting CMOS due to virus

Question

I have Toshiba 1135-s125. I got a CMOS virus somehow and need to reset it. I attempted to open case but even with screws out can't get it off. Can someone tell me either how to finish the cabinet removal, or how to reset CMOS without opening cabinet? Just to let you know, virus made the normal boot sequence force to IPX boot, which I can't use.