|There *should* be a jumper. It would be labeled JP1 & would be right next to the battery.|
To use it, 1st unplug the power cord, then move the jumper cap from the normal position to the clear position, wait a few seconds, then move it back.
If there is no jumper, unplug the power cord, remove the battery, wait a few seconds, then replace the battery.
Why do you need to reset the BIOS in the 1st place? And are those specs correct? You're running XP with just 64MB RAM?