|According to the manual, the 1-2-3 lights mean:|
"the operating system is attempting to boot from a device (such as the floppy drive or hard drive); check system setup to make sure the boot sequence is correct for the devices installed on your computer."
So the error has nothing to do with peripherals, RAM, CMOS battery, video card, sound card, etc. Run thru the BIOS settings & make sure everything is dialed in correctly, especially the boot order. Depending on what you have, the order should be - floppy, CD/DVD, HDD. Then open the case & double check the cables to all the drives. If the system still won't boot, it's possible that the HDD has failed. Try booting off a bootable CD or DVD & see if that works. If you have a Linux disc, boot off it & then see if you can view the contents of the HDD.