Corrupt hard disk no longer detected at all.

My 500GB Western Digital SATA II hard disk recently became corrupt out of nowhere. One day I turned my computer on and it would get up to the windows xp loading screen and then go to a BSOD with error code 0x0000007b. I kept pressing the reset button but nothing worked until i shut it off completely and then turned it back on which allowed it to work but it took forever to load into windows. Then when i brought it to college it acted up again but with the error says "Windows cannot read the selected boot disk, please contact your system administrator." So i ended up reinstalling windows and i noticed that while installing xp that my master hard drive was not there to be partitioned, only my primary slave drive. So i was forced to use that one instead. I check into my computer and my master hd still isnt there and it isnt in the BIOS either! Please help me!

Well I dont want to lose all that data. I have so much stuff on there that I really need for college and for personal reasons. Ill try switching those things.