Context menu extra wide

My brother-in-law brought his laptop to me "to look at..." with the complaint that when he 'right-clicks' on an file ornay other 'object', the context menu that appears is VERY wide...
In fact, so wide that it's sometimes difficult to 'follow' across from an icon on the left side of the context menu to the corresponding 'menu item' on the right.
Depending upon location of the item he right-clicks on, his context menu can consume almost 50% of the screen width and STILL not fully display the enire menu option properly!
How has he done this? More importantly, how can we 'restore' it to its normal width?
I've read about how things like 'picozip' and WinRAR can sometimes affect the context menu, but he does not have these installed, nor apparently were they ever installed.
We've scanned for virus and spyware with installed software (Norton Internet Security 2009 and Spyware Doctor) as well as performed 'online scans' from several sites, and nothing 'shows up', so it seems as though this is some sort of registry affectation of maybe simply a 'system setting' that has gone awry.
Does anyone have an idea as to how I can 'fix' this, short of 'hosing off' the entire hard disk and 'starting from scratch' (albeit, the way his laptop is operating, this might not be a bad idea.. Plus, his hard disk is pretty cluttered and pushing what I consider to be the 'upper limit' in the amount of consumed space. I think I'm going to try to convince him he needs a larger disk, anyway...).
Any help?