How can it be a video card issue when she is able to go on just fine in a different account?

I would suggest a system restore even if it is just back a couple of days. Can't hurt anything to at least try.

She can also run Windows XP's system file checker to check and restore various system files that might have been borked in some way.

dont use system restore ...


Generally SafeMode uses basic hardware to run windows, with the information you gave me its a software problem, most likely with the video card. Black screen can be many things, commonly? With the information you gave me, could have been a dual monitor setting that was enable in which the laptop screen wasnt the primary monitor, could be bad hardware in which the account is loading separate hardware, be a little more sepecific on the accounts... which ones work and which ones dont? Id suggest going into safemode, uninstalling the Video card and re-installing it...