She already said she'd tried changing the screen size.
Odds are that a game would adjust your screen resolution, its easy enough to rectify.
As above, Right Click on your Desktop, choose Properties, then if its XP i think it comes under Advanced (whatever its usally the far right tab), then there'll be a slder towards the bottom set to something like 640x480 or 800x600, move this to the right to increase your screen resolution and click Apply/OK.
Should be sorted, just depends on exactly what resolution you want to go for, on an older system probably 1024x768.
HTH
Gavin
December 2008