Help with unknown pc trouble

hi im having a problem with one of my pc's. when i turn it on it doesnt seem to boot into windows, then i tried changing the boot drive in bios to cdrom for it to boot into windows setup and reformat it, after doing it so it restarts then nothing happens just beeps over and over short beeps to be exact i tried pulling of the ram, vidcard and it still beeps. after leaving it turned of for awhile it goes to post but doesnt boot into windows. then one time it showed me checksum error and wont boot then i left it off for awhile again then cycled back to post and no boot to OS again, im totally lost i dont have a clue on whats the problem thanks in advance

hi thanks for the fast reply much appreciated man.

first the last time i remembered it was working fine was like 3 days ago my friend was using it he said he was just on facebook playing a game then it suddenly went fatal error (blue screen of death lol) then i went to sleep that night and decided to tinker it the next day. then next day as described above was the scene. I haven't upgraded anything yet its still in its condition when the first time it was assembled 5-6 years ago. i also havent moved it. well i also haven't experienced any power shortages and or spikes. by the way before that pc worked i changed it with a 500w power supply because the last time it broke like 3 weeks ago the PSU wasnt giving any power to the board so decided to buy a new one instead and worked fine until the above problem happened. yes it is overclocked by 153 since its maximum is 163. well i have 2 more identical pc's like it and the others are working fine with the said oc's. i hope i answered some of your questions man thanks in advance for sharing some info tc.

glhf

p.s. sorry for my bad english.