My dell shows its running on the batteries ( or battery) when its plugged into the wall, ? however it will not run on the battery when unplugged ? I cannot do bios updates, servicepk2 update or anything other than general windows updates without the ac adapter being recognized as in use ?In bios everything looks ok, ( batt. wise) I am out of ideas.?

Batteries may be dead or going dead. Are you still under warranty?

not under warranty, the lap top was givin to me , by a customer who did not want to replace the hard drive, so i took it, put 40 gig hd in, and have been using it .would the batteries still show " discharging @ 98%" in power management (win/cntrlpanl) also in bios shows batteries are still at 99% ??????

Thanks..

You can try taking out the batteries and blowing condensed air inside the battery slot to remove any dust etc. Also clean the contacts on the battery