I'm in trouble again. Earlier I said that I had set up a portion of my primary disk (Drive C

and installed Windows 7 on it. When booting, I had the choice of Vista or Win7. But, when in Win7, I could not access anything on the C: drive. So...
I installed an old 40 GB hd on my PC. My primary HD is a sata 360 gb. Once installed, each time i booted it got disk failure errors at startup saying a disk had failed, but when i hit f2 it went ahead and booted and I had both HDs available and accessable in Vista.
I installed Windows 7 on my 40 GB hd. Then, when it was totally installed, when I boot, the BIOS does not see my 360 GB hd, only the 40 GB hd and my choice of booting from Vista is gone. When Win7 is loaded, I can see the drive C: but cannot access anything on it. When booting from Drive C:, I can access the 40 GB drive, whi can't it work in reverse?
What do I do now? How can I get the BIOS to see the 360 drive again? How can I get permission to access my C: drive when booted in Win7 from the 40GB hd which is now drive J:?
Do I have any option other than removing the 40 GB hd from my PC? How do I unisnstall the Win7 from it before removing it? How do I uninstall Win7 from the allocated portion I first installed it on?
I would love to continue using Win7 but I have to be able to get to my applications and documents on the C: drive.