There are electronics inside the case that are very susceptible to electrostatic discharges. To protect your computer, touch the metal of the case to discharge yourself of any charges your body may have stored before touching any of the components inside. For this procedure you must turn off the computer, we suggest that you unplug it from the wall outlet as well.
Removing the CMOS battery is one of the two ways to clear the CMOS settings. The other way is to use the jumper, you have mentioned seeing these, so you know where this is located. There are three pins in this location, the jumper in the normal position will cover the middle pin and one of the end pins leaving one of the other pins bare. To clear the CMOS you need to move the jumper so that is covers the middle pin and the other bare pin, this must be done with the power off. After a couple of second you will replace the jumper to the original position.
Try using a bootable CD like you XP installation disc and see if the computer boots from it. You may need to change the boot order in the BIOS so that the CD-ROM is the first device in the boot order. If it is able to boot from the CD this will point toward the problem either being the OS or the hdd.
Hamluis, If your settings in the BIOS are lost when you turn off the PSU by its on/off switch this indicative of a bad CMOS battery. The battery should save those setting when the power is turned off.
Edited by dc3, 25 June 2008 - 08:45 PM.