I found that if I start the computer with only the power supply and wait till windows is fully operational, then insert the fully charged battery, windows will keep on working but the battery indicator icon has a red cross through it, even though I have the battery green light.
When the laptop is locked up, the hdd light might give out a tiny flash occasionally, and if I brush my finger across the mouse pad and wait, the curser may move a little bit after several minutes.
So it seams like it's in a super stall mode rather than lock up and Alt + Ctl + Del does nothing.
I don't want to tell my sister to buy a new battery if that's not the fix.
Ideas anyone ?