Computer won't boot, shows blank screen.

[kgsauls]

Before you redirect me, understand that any amount of googling did not yield results to my problem.

I have a thinkpad edge e420s. I had windows 7 on it, and something went terribly wrong. My icons started to disappear, and windows search was no longer working. I think I messed up the permissions somewhere, so I decided to install windows xp. When trying to boot from the disc, I was getting a blue screen error right when the installer was trying to start after loading drivers. I found out that xp might be conflicting with the sata hard drive, so I went into bios and looked at hard drive settings. There were two options, "AHCI, and Compatibility". I figured compatibility might solve my problem, so I selected it, saved and exited bios, and then nothing happened, it just stayed on a black screen. Let it go for awhile, and when it was at the point where I knew it wasn't doing anything, I turned it off. Now when I try to power it up, I just get a black screen, no splash logo or nothing. I tried disconnecting the cmos battery and internal battery, let it sit for awhile, but nothing is fixing my problem. Are there any secret key presses that I can hold down while I power up my system to reset the bios to factory defaults? Otherwise, am I screwed?

If you got to this point, thanks for reading. If you can help, pleaseeeee help me. Thanks