Weird sound on pc

Hi, when I got back to my office this morning and when I switched on my computer I noticed a strange sound coming from it. I did all my work without taking great consideration of the noise but suddenly my pc froze up and when I tried to start it up again it would not. The sound was like if the fan inside was running very quickly. Anyone help me please I have some very important works on that and my boss will be very angry if he knew that I have lost all the data on it.