For the CMOS BATTERY. It's the usual CR2032 coin battery. Look for a CMOS RESET jumper and reset it to get back in. No reset found? Remove the AC cord, then the CR2032 coin battery, then do an errand. Put the battery back in and try again.
Okay so i was upgrading to windows 7 last night i rebooted my computer it went past the logo then the 1st message was "BOOTMGR is compressed, press Ctrl+Alt+Delete to restart" i did this for about 30mins. then went on my dads old windows xp to find a recovery disk download (since mine came pre-installed and i don't have one" but before i put the disk in i went into BIOS and messed around with the settings then my smartness disabled all devices i.e. floppy, hard disk, cd rom, usb, and optical then saved it exiting BIOS then a new message pops up "A bootable device cannot be detected please refer to User Guide" then everytime i try to restart it and try pressing "F2" bios settings it won't let me get back in what can i do? please help
also my system is: eMachines W3611 Windows Vista Home Basic SP 2 with a SATA II 160GB HDD, Intel Pentium 4 Processor 631