Abit Phoenix bios change - help with beep then power off

[cpufox]

Abit KN8 nForce 4 Motherboard (2-3 yrs old)
I was given an abit Windows XP system which has been functioning quite well for some time.
In the last month, I'd occasionally get BLUE screens (MACHINE EXCEPTION ERROR), where the text suggested repeats could be fixed by removing new hardware (really hasn't been any)...or by turning off shadowing, cache options via the BIOS.

I went into the BIOS and made a couple of changes which did not appear to relate. One change, which likely caused by problem, was setting the % speed of the CPU FAN from MAX to a %, to allow the FAN to adjust it's RPM to accomodate the CPU heat generated.

I set it to 80%, did an F10 SAVE. Just following this change, the system powered off. Now each time I boot, or try a power reset (e.g. power plug removed, off for many minute, then power on OR via front power button), I hear a speaker "bee-up" sound, and then soon after the system turns off. It does this each time, not allowing any time for post or "any" message on the screen.
It stays on approximately four sections, then shuts down. I've tried power on from strip, back of system, button in front, even holding primary button in front, while simultaneously "pushing in" a small button, just below the power (hoping it would reset BIOS to default). Any suggestions for resetting defaults, getting out of this predicament. I really want the system bootable, and can live with the infrequent blue screens. I don't have details on this "white box" (it's a black case, red light via plastic cover, lower to front chassis). Open up, any way of resetting BIOS to default via dip switch, etc? any ideas are welcomed...

Please reply. You can also email cpufox at gmail dot com. Thanks!

HELP! Anybody with ideas?? THANKS Agent, I'll see if I can reset via battery

[Agent]

To reset the BIOS there will be a jumper on the motherboard itself. Its usually by the battery, but it can be anywhere.

If you can't find it, just pop the little battery out for a bit (make sure the power cable is unplugged too!). That will reset it to defaults

[TAKTAK]

To reset the BIOS there will be a jumper on the motherboard itself. Its usually by the battery, but it can be anywhere.

If you can't find it, just pop the little battery out for a bit (make sure the power cable is unplugged too!). That will reset it to defaults

why with the two threads?? here and here
just one will do the trick.

do as agent says, and you won't go far wrong.