|Your optical drive may have an issue booting to a DVDR. Why did you use a DVD instead of a CD?|
If the PS/2 keyboard doesn't get you anywhere in the POST screens then you might have a BIOS issue. Is there something more you haven't told us yet?
Do you see any of the configuration screens during the POST? If so, what other keystrokes are mentioned in those screens?
The message you are getting is generally related to hardware issues. If your keyboard is not causing any response from your computer try a different keyboard, if available.
Disconnect all external drives, printers, scanners, card readers, etc.
Sometimes that message appears after the BIOS has reset to defaults. That can happen when the CMOS battery on the motherboard is weak or dead. That is why jam has advised you to change that batery. However, the fact you can't access to BIOS screens is puzzling. Even with a dead CMOS battery you should be able to access the BIOS with a PS/2 keyboard.
Are there any lights on the keyboard when booting? Check the cable to tower. DO NOT change a PS/2 keyboard or mouse while under power.