Put 1 stick of memory in, then remove the on board battery, and move the CMOS jumper pin to reset the BIOS. If you can boot up run it for 10 minutes and then add another stick of memory. Make sure you are mounting them in the proper slots.
If this doesn't work you probably wiped your EEPROM chip. You may want to go here for information on a new chip http://www.biosman.com/