|RAM can absolutely stop you from being able to POST. What kind of RAM do you have in the system? |
If you ran the CPU with no thermal paste for a certain amount of time, you may have fried the CPU. If it was only for a second, LIKELY there was no damage, can't say for certain. Now, normally the thermal paste comes on the CPU fan, if you used the stock CPU fan to begin with, then you shouldn't have needed to apply thermal paste. Answers to the questions in #1 and #2 are important answers. If you purchased a third party CPU fan, depending on the model you will need to apply thermal paste.
Like fingers said, go with the bare minimums. Take all the parts out of your case, put the motherboard on the motherboard box with 1 stick of known working RAM that is compatible with the system, the motherboard, the CPU & fan, PSU.. IF you dont get post, shutdown, pull the RAM out, and boot up.. the motherboard should beep. If it doesn't, I would RMA the board, and the CPU.