My battery on dell died after 7 months (warranty was 6 months so exactly 1 month after it's warranty on battery expired)...
I've ordered a cheap replacement one for $35 from
DX (with bigger capacity) and it simply rocks now... My battery life is better than with original battery and it works perfectly for over a year now...
In most cases it's not the problem with OS than with battery manufacturer making it to simply stop functioning after some period of time (
planned obsolescence)