You'd need to leave the CMOS battery out a little longer usually to reset the CMOS. There might be a jumper on your mobo to reset the CMOS and NVRAM with which would be much faster than removing the battery and waiting. Are you sure you didn't accidentally knock a power connector off the mobo when you were inside the case? Checked all of your connections?

If none of the above works remove everything you can from your box (sound, NIC, etc.)and try to run with minimal hardware installed.