weird M5200N problem?!?!?!?

ok this is the problem. Ever since the hurricane hit florida (yes, again) couple days ago I lost power. So I try to run my laptop on battery (this is not the first time i run the laptop on battery but so it just started). But then i notice this weird sound comming from the CPU area of the computer (i won't say it's the cpu but it's from that general area, it's like this ddding sound (sounded like it's processing something it's like ddding .....ddding....ddding..rather steady with pause in between). And the weird thing is it only make the sound when i use the battery, whenever i plug in AC power the sound stops right away or if i run on battery but with some USB device pluged in it stops as well. I'm starting to think this might be a glitch in the OS so im thinking about format harddrive and reinstall the OS but then that's just a pain in the ass. Other then that the laptop runs just like before...so anybody think they know what's going on?? please e-mail me if you know the solution im going crazy with this problem....