Removing the battery for a couple of minutes or so and putting it back should reset the bios/cmos back to default settings allowing you to power up and get into the bios again to reset whatever needs to be (such as disabling on-board video if you have it so that your AGP card will be the default if you also change the bios to look at the AGP slot instead of the PCI one at first boot). If you have on-board video and made changes to the bios, there is every possibility that the bios defaulted to the on-board video which you don't have your monitor connected to...and that is causing no video on the monitor right now.
You can, instead, jumper the CMOS three pin jumper to the OFF position instead of the ON position for a minute or two, then position it back to ON, and reboot getting the same results as removing the battery. Those pins are identified by imbedded print on the motherboard if you can't get to the manual immediately. If the three pin connection has a jumper in the 1-2 position with the third pin bare, move the jumper to the 2-3 position....if it's jumpered in the 2-3 position with the first pin bare, then move the jumper to the 1-2 position instead.
Some say to power the system up momentarily with the jumper now set to the OFF position, then power back down to move the jumper back. Others say you should never power up with the jumper in the OFF position. I've done it both ways with no ill effects.
Keep in mind....NEVER make multiple changes in the bios at the same time. It's always best to make one change at a time, reboot the computer and make sure all is well. It's easier to trouble shoot exactly what the last step you did is that caused the problem.
i just upgraded from a voodoo 3 to a ATI AIW 9600 so i was very happy to see the new performance of my computer, i also added two extra fans so i thought i would go and overclock my pc. My mobo is a chaintech CT-7aja0 with an AMD Thunderbird 1.01ghz, they were nice enough to include an easy overclock method in the BIOS and so i thought while i was at it i could tweak up a couple more things... riiiight ... so i went to a couple menus in CMOS Setup Utility at boot... In Advanced Chipset Features, i set the Optimized Defaults (which only seemed to change modem from disabled to enabled). I did the same in Advanced BIOS Features which made this change, my first bootable device was still floppy, second was still HDD-0 but my third had changed from CD-ROM to LS120 i thought it might be some sort of booster !?%^*#!, the computer should know better than i... i had read that OCing is to change the voltage basically so i also did that from Frequency/Voltage Control, i changed PC100 +0.5 to PC133 +0.5 ... i booted and nothing! i checked with a computer whizzer (than me) if i was right about this procedure being OCing and i turned out to be right, even though im still not to sure if i have to flip any switches on the mobo also... now here is the results i got...
1. floppy does not test at boot.
2. hard drives do test and so do CD-ROMS
3. processor does some work then stops working after a minute or two.
4. i cant see what that work is because i have no display output! (not even a c: prompt)
5. monitor stays on standby mode (light flashing)
6. im guessing processing doesnt get to BIOS start because keyboard does not respond (num lock is off)
7. windows install CD does not make any difference to the boot.
8. nothing to do with my AGP ATI, i tried putting the voodoo PCI back in & no display still
after thinking about it for a while and asking some people my friend said that i should take out my battery from the mobo (not the PS) ... im at work now so i wont be able to test out that theory until 8 hours from now so if anyone has any other suggestions please do throw one because the more i get the better i'll feel (my heart beats differently when my computer is not operating properly i feel like im having a heart attack at 22) ... thanks in advance.