Laptop problems

HI Guys,

I have a laptop at home, decent spec bought about 2 yrs ago. It is my mothers. The power at the house has gone off a few times while the laptop has been plugged into the mains and now the laptop appears to be buggered. It will only run when she has the power supply plugged in - if she tries to run it from battery then it runs through the normal boot process but crashes and restarts before windows kicks in and just appears to be stuck in this loop - if the power supply is plugged in it boots fine. Also - it has a dvd writer in it - but it will no longer read CD/DVD's. It also tells her that the hard drive if full - when there is clearly alot of space left on it.

She's taken it to a shop and they have told her that its the motherboard thats gone - i just wondered if you guys would assume the same or if you think it could be fixed by replacing the batt & HD..??

Cheers