I'm not sure what you mean but I assume you mean the forum page is wider than your screen. If that's the problem this is an easy fix and there are two:
Change the resolution of your display. This is done by clicking :
START, CONTROL PANEL, APPEARANCE & THEMES,
CHANGE SCREEN RESOLUTION. Then slide the screen resolution arrow all the
way to the right. Then click OK
OR
if you're using Internet Explorer and your screen resolution is already set to the highest. Look in the lower right hand corner and you'll see a small plus sign "+", a percentage number, probably 100% and a little triangle \/ - click the triangle, select CUSTOM then type in 90% (depending on your setup the number might not be exactly correct - simply change it until the forum fits exactly within your screen.
That should handle the problem...