was cleaning the fan on my spare computer cause it was clogged up but when i went to start it, it powers up and fan is working ok but it wont boot up( was working 5 min earlier)it doesnt even beep, so i tried a diffent fan but still no joy.
On older systems, working around the CPU area can readily result in contact problems with the CPU and its socket.
You should remove the fan/heatsink - lift the CPU locking lever and press it back down again, 3 or 4 times - at the same time gently pushing the CPU into the Socket. This cleans the contacts, which operate with a wiping motion when the lever is moved.
You'll then have to clean off the old thermal compound from the CPU and the heatsink, apply a very thin film of new compound, then refit the heatsink/fan. That's always cleared this type of problem for me.
It's also possible you may have disturbed the RAM, which is next door. This can be removed and refitted too, which usually clears any problems. But do the CPU first, as it's the most likely culprit.
*where can i buy the cpu paste from and how much.*
A computer shop
*why does it not beep.*
The beep is to tell you is has completed all it's power-on self-tests (POST) succdessfully. If it doesn't beep, then they have failed.You don't always get an indication why they've failed, depending on exactly what failed and when and how.
Good luck with trying out the suggestions. Take care, and don't forget to unplug or switch off the mains before starting the work. That's not to protect you, it's to protect the components. Just switching off normally is not enough.