Win NT Server Crash

I was completely surprised to arrive at office, seeing a black screen on my NT server. The message there reads “No operating system is found”. I have a backup tape using Veritas Exec.

My questions are 1) what could be a cause of this problem? 2) What is the best recovery method?

My purpose is to recover complete data before crashing, not from the tape backup which is not so updated.

Appreciate all helps.