If your computer can't read the date from the drives, they were probably set up as RAID 0 or the drives are not any good. Do the drives show up in the BIOS?
There's not really much info, but you may also want to try using a Live OS. If you use Ubuntu it will allow you to run the OS off the CD. If it works fine, it's either a software problem or a hard drive problem.
This is normal for Windows Vista/7. These versions of Windows store commonly used data in the memory so that programs that you use a lot will load instantly. Of course all of the memory that is not in use is still available.
Just pull the card out and enable the onboard video.
I'd try to find another PSU to test.
Apevia is terrible. I've seen one that took out the rest of the computer when it failed.
Re: Custom built computer randomly memory dumps and restarts. RAM not on MOBO QVL lis
Run memtest and return your memory for a replacement if it finds errors.
Your heatsink/adhesive is may not be making contact with the CPU which is causing the CPU to overheat. Also make sure you connected the fan to the CPU fan connection on the motherboard.