Thinkpad 600 battery boot problem

[Geronimoknows]

Hi all. I have a Thinkpad 600 that i am trying to bring back to life. I have managed to install windows 98 on it, but i am unable to install windows XP properly. I noticed that the bios file is old. Unfortunately, i am having an issue with upgrading. The laptop is peculiar in that when i put in a battery (i have no idea if it is dead or not) the computer will simply not turn on. I will press the on button and there will be no post or anything. But if i take the battery out and just run it from the plug, it works fine. I have found some methods on how to upgrade without a battery, but i have gotten errors such that the laptop thinks that the battery is in, but the it is unplugged. Windows 98 correctly registers that it is plugged. I am willing to buy a new battery, but i have no idea if it is worth it. If anyone has run into this error, i would greatly appreciate a response.