It won't display on the monitor!!!!!!!!!!!

Hello,

I have had my computer for 5 years and not a single problem until now. See, I came to my friends house to set up my hard drive there but he has a different monitor than mine and I need to know why my hard drive does not work with his monitor (ps i have not used my computer for 2 years). I have tried everything unplugging it and holding the on button, changing the monitor's screen resolution, nothing just a black screen. What should I do (his monitor works just fine)? And could my Mobo be a goner? My computer will boot and the fan will run plus I was able to take my a video game out of the disk drive. When I plug in the monitor all it says is "Moniter going to sleep". Thanks in advance.