If you see the POST error in the picture on your IBM Thinkpad 600X's screen, your BIOS battery is probably dead. BIOS batteries for Thinkpad 600Xs go for $40.00 online. However, the actual battery is simply a common lithium watch battery with a special (expensive) connector. I will show you how to carefully remove the connector from your dead battery and attach it a new watch battery purchased for $5.00 at Radioshack.
Parts and tools:
1x dead Thinkpad BIOS battery
1x CR2025 watch battery
1x Roll of packing tape
1x Sharp knife
1x Needle-nose pliers
Step 1: Get a new battery and remove the old one.
Get a CR2025 lithium watch battery from RadioShack.
Remove the dead BIOS battery from the laptop. It lives in a little holder next to the RAM on the bottom of the Thinkpad.