monitor switches off

Hi!!

My systmes gives following problem.

The monitor switches off while the booting process only.I am using
win2k and when the screen changes from initial boot win2k screen to
the drive file configuration consisteny black screen the monitor
switches off.I have to again restart the system and then everything
works fine.

What could be the reason behind this peculiar behaviour.??

regds,
Yogesh Joshi