A150D Battery problem

Hi guys first post but i need help, i have an A150D just over a year old and has windows 7 on it.

Had no problems at all until about 2 weeks ago, charged the unit up for the first time in a while (there was charge in it but not much) now the damn thing loses the charge within a couple of days when turned off and i mean totally flat.

Unit runs fine when charged no noticable problemsapart from seems a tad slower since i put windows7 on.

Any ideas at all, battery life is usually about 6 or 7 hours with no problems and has been since i bought it.

Thanks in advance and apologies if i have missed a previous post on the same subject.