If you over-clock your CPU you run the very real chance of it overheating. Contrary to popular myth, there is nothing in a computer that will enjoy running over 35 degrees C and many processors run at closer to 50 most of the time, which for any chip is asking a lot. the same applies to your PSU and yes parts of it may still run the low current components on the board but it may well have cooked the main regulators and be incapable of giving anything enough current to actually run.
When you select a PSU for a computer, I strongly suggest you over-rate it by at least 100 watts based on the total requirement from everything on the system. This calculator is pretty good at keeping you out of trouble in that area. Under-rated PSUs are the main cause of most failures in stock equipment,.. trust me, I've spent 35 years fixing them.
You have probably blown the CPU as well, with heat and probable voltage spikes when the PSU fried.
If you really want a faster machine, do not over-clock the CPU, buy an serious upgrade, it works out a heck of a lot cheaper than replacing cooked ones that the manufacturers will always tell you "over-clock at your own risk",.. and for very good reason!