Resetting the CMOS is a good idea at this point as Mister Sprinkles has already pointed out.
Also check your BIOS to see what storage driver settings you are using, IDE, AHCI or maybe even RAID, unless you which drivers you had selected in the BIOS when originally installing windows, just try them all and see which one works
Assuming your are using SATA Hard Drives then AHCI would be your best option, if your going to do a clean reinstall windows anyway from scratch then just make sure you have AHCI selected before you do the re-install booting from your disk or USB drive, assuming you want to keep it simple and don't have need to setup the system using RAID drivers like you would use if you where setting up a data server rather than a home PC.
BTW have you got windows on disk or stick? if not try getting hold of this to see if you can still boot from your disk or stick, the HD maybe salvageable even if the data has been corrupted to the point where you will need to reinstall windows, you may still be able salvage the drive during the reinstallation via deleting all your partitions and running a full format, in fact if you find that setting your storage drives to IDE in the BIOS starts your system and your Drive is SATA, then personally I would do a complete reinstallation of windows anyway just to change the storage drivers to AHCI, once windows is installed there is no going back to change your storage drives from what you had selected when you installed windows, so again insure you have AHCI selected in the bios before you start a re-installation, unless you are in fact still using an IDE drive in which case you have no choice but to use the IDE drivers.
Also the fact your PC is able to "power up" does not prove your PSU is functioning correctly, each rail running to power anything been powered in your system has to be exact, if your rail is suppose to give you 12v then it has to give you that exactly constantly or else you will suffer failures that will make you question every possible component within your system, having wrongfully decided the problem is not the PSU based purely on the fact that your system powers up, when this could easily be blinding you from the real issue if it is the PSU at fault, when although you still have power, or at least think you do, that power is not been regulated by the PSU along the Rails correctly at the constant level of accuracy that every component within your system demands without exception, this been the case your PSU is the problem.
If you take it to an engineer repair shop, you could have then test the PSU for you very easily with a multimeter, such an easy task in fact if you have the right tools that I can't even imagine them charging you for testing it out, especially if you are there willing to buy a PSU from them if needs be, and make no mistake, if the PSU is not regulating the power output correctly you will need a new PSU.