Which operating system? Reset the CMOS by removing the nickel-sized battery on the motherboard for about one hour. Put back the battery and reboot PC.
Any light at the NEC's LED port?
Remove all optical drives from Device Manager. Do the same to the primary and secondary IDE controller. Reboot and windows will reload the appropriate drivers.
Did you scan the hard drive for problem? Last option is to wipe the hard drive and reload windows.