|Did you unplug the AC to the PS, or otherwise switch off the AC to the PS or the computer, AT ALL TIMES, when you were fiddling around inside the computer? If you didn't, you may have damaged something - ATX mboards are always powered in some places even when the computer is not running, as long as live AC is being supplied to the PS, the PS switch is on, and the PS is properly plugged into the mboard.|
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
The mboard probably requires an extra power connection from the PS other than the main 20 or 24 pin connector, and the video card may require an extra power connection from the PS - did you remember to plug that/those in?
If you moved a jumper to clear the cmos, did you remember to move it back to the "normal" position?
The cpu fan must have either 3 or 4 wires, it must be connected to the 3 or 4 pin cpu fan header on the mboard, and it must be connected to the right pins. If that is wrong, usually the mboard boots anyway but the mboard shuts down in a few seconds when no cpu fan rpm is detected by the bios, but in theory it's possible the mboard may not boot at all when no cpu fan rpm is detected. Sometimes there is an alignment tab on the mboard header that is easily broken off or bent - if that is missing or bent, it may be possible to install the connector from the fan on the wrong pins or the wrong way. A 3 wire connector from the fan must be on specific pins on a 4 pin mboard header - see the mboard manual.
There may be a poor connection inside your case somewhere.
Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main connector/socket should be more or less perpendicular to the mboard surface rather than at an angle. Make sure all cards in slots are all the way down in their slots.
While you're in there, if the cpu fan/heatsink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components ) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. If may be difficult to clean the top of the heatsink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
The ram should work fine in any AM2 or AM2+ mboard, but
- if the ram you have installed is not the ram that was in it when the same mboard worked fine previously, we have heard of people having problems with G-Skil ram,
OR - the ram may have been damaged by something you did.
If your problem is caused by the ram not wanting to work in this mboard, or by the ram having been damaged, that is easy to check for.
Make sure you have a speaker or speakers or the equivalent connected to the mboard so you can hear mboard beeps (see your mboard manual if you need to).
Remove the AC power to the case/power supply.
Remove all the ram.
Restore AC power.
Try to boot.
If nothing else is wrong, you will get no video but you will hear a pattern of beeps that indicate no ram is installed, or a ram problem.
E.g. for an Award bios or a bios based on one, that's often a beep of about a half second, silence for a half second, a beep of about a half second, silence for a half second, continuously.