HP laptop issues... help!

My coworker just told me that she’s having troubles with her laptop. Apparently, when she tries to turn it on - it begins to boot up but then quits - so it won’t even turn on. She thinks the battery is dead but when she plugs in the charger - the light on the charger flicks on and off (like it’s charging, then it just stops, then it starts again…). Moreover, there’s a DVD in it - that she really needs to return to the rental place:doh:. I really don’t know very much about this type of stuff - but to me it sounds like she’s got a bad battery. Does anybody here have experience with this type of thing? If so, what does she need to do to fix the issue?