Cmos batery Dell Insprion 5100

Where is the CMOS battery located in a Dell Inspiron 5100? I took apart the case but can't find the battery anywhere. I have heard it is possible to be where the screen is as well. I looked all over Dell websites and forums but none of the service manuals show anything about CMOS.

FYI the reason i need to find is the computer had a corrupted registry. I got into BIOS by pushin f2 and booted off of an xp disk and used recovery console to repair registry. Was able to log back into computer after BSOD would not allow me to before. Still followed the KB articles and needed to boot back up from cd. Only problem is i set boot order in BIOS but it wouldn't boot from disk. I hit F2 again to get into BIOS and got nothing. It won't load the BIOS. I was able to fix my problem by installing recovery console on the machine but can't get to BIOS now. Figuring that resetting the cmos would help. I tried external keyboard as well but no dice. All keys work and are fully functional after the computer boots up. I can hit F8 to get to safe mode options as well but not the BIOS.