I am jumping the gun here so try these things last....
While you are at it trying all the great suggestions, check to see if your hard drive is in compatibility mode by going to start>run>msconfig>advanced> and see if "force compatibility mode acces" is checked.
It could be possible that your ide drivers are not initializing for whatever reason.
Bootlog analyzer can usually tell you this.
If you uncheck the compatibility mode box (if it is checked) and restart, it might fix the problem, but if your ide drivers don't intitialize, you might have to go into safe mode and edit the registry to be able to boot back up.
However, if it is not checked, you can check it and restart. If you comptuer boots up normal, then you might be on to something.
does your motherboard have an intel chipset? Or an Ali.
If it has Intel, you may have to run the ultra dma installer.
plus check out device manager