You can find all the drivers for the machine online - just head to HP.com and enter in your model number in a driver search. You can, however, reinstall the OS she has on the notebook by getting an OEM version of whatever OS is on there and using the CD key on the bottom of the notebook. You can get the disc from a torrent or whatnot.
Notebooks are very the same as desktops software-side. Don't panic.
If the machine is running hot, take it out to the garage and give the heatsinks a blast or five of compressed air. Dust accumulates inside the heatsinks (like in desktops, but there's less space, so it happens faster) and clogs them up.