when my computer was getting slow and i was told to replace the battery in the cmos so i did and then i found out it resets all defult setting or somthing and then the computer started stuffing up making funny noises when restarted and now i cant even get a picture its just black and nothing appears what can i do here? or if so what do i need to replace i know its not the monitor is it the cpu or what?

You may have dislocated the graphics card while replacing that battery (which always resets your BIOS back to basics).
Check that all cards and cables are properly seated/connected, then try a start. If it works, check your BIOS if you want/need to change anything.

If it still does not want to start:
did you change any parameters in the BIOS after you replaced the battery? If so, there is basic help available.
Look in you mobo-manual for a jumper or contacts/pins that can be used for resetting your BIOS. If you can't find those, just take the battery out and leave it out for about 20 minutes, then reinsert it. Make sure you don't break any legs or supports for that battery.
Restart the PC, let it boot into windows, then restart again and go into the BIOS to make the changes that you want/need.

Sometime in the bios the default graphics card is pci
so if your using an AGP video card and your bios is set for a PCI card it will not recogize your card.
My ASUS mobo under advanced integrated peripherals has the setting Primary VGA BIOS (default setting PCI)

RG/DTG,
those BIOS settings are only relevant if you would have both AGP and PCI graphics cards in your PC. That setting only tells which BUS to look in first at booting up. You may shave 1-2 seconds off your booting time by setting it to AGP rather than the default PCI if that is your card. As long as there is a working graphics card in it, that PC will start, regardless of BIOS-setting. (always assuming there is nothing ELSE wrong).