I recently took my desktop computer out to blow out the dust that has accumulated inside. Then i brought it back and connected everything and closed the cover and pushed the button to start the computer. The fans do come on, but it sounds like its spinning at its highest possible speed. The monitor does not come on, there is no beep nor anything that comes onto the monitor, the CPU, the hard drives do sound like they're coming on and the CD drives operate normally.
The power light is on, but when the computer was working, it usually stays off until I put the computer into sleep/standby mode.
I have tried a lot to fix the problem through research on the internet. I have tried swapping out my power supply, disconnecting everything from the motherboard except the memory, cpu, heatsink and fan, power supply and their connections to the motherboard, and graphics card. Still, the machine powers on but with the same issue.
I have tried swapping out the memory but still nothing happens.
I have tried taking out the cpu and then putting it back in and that solved the problem (Windows XP loaded and I could use the computer and sleep the computer), until I took out the heatsink and cpu fan to reapply some thermal grease onto the cpu. Then reattached the heatsink and cpu fan and closed the cover but then it had the same problem again. I have tried to again take out the cpu and then put it back in, but still the same problem.
Any suggestions to what might be the problem with my computer? Thanks in advance!