My D410 will charge battery but wont run off it

hey everyone, ive just been trying to build this D410 for my moms boyfriend. i bought the bottom half of the D410 from an ebay seller and peiced together the rest. the system seemed to work fine with its existing hard drive it had an install of xp and it booted up. i was waiting on a dvd drive to reinstall Xp and a battery. but in between i bought a media base complete with dvd drive and battery.

well the battery worked fine in teh media base, it charged and supplied the laptop with power when i disconnected the laptop. Then i popped the battery into the laptop, the laptop charged the battery but when i yanked the cord the laptop went off. I tried powering the laptop back on but no luck. I tried disconnecting the battery and taking out the cmos battery and that didnt work. i tried everything i could think of including making sure the screws were on tight so it was sure to make contact all the way. I cant figure this out.

what really chaps my ass is the fact that when i checked the bios the system had a service tag # and to my surprise the service tag had almost 2 years of warranty including Gold Service left on it! But because i didnt have the express service code or an order number i couldnt put the warranty in my name!

anyways any help guys would be greatly appreciated.