Right click on texmod, go to properties on the menu that pops up and left click, now find the tab along the top of the new pop up called compatibility and left click it, now all you need to do is left click on where it says 'Run this program in compatibility mode for' to place a checkmark and then click 'Apply'. ;)
This is for windows 7, vista should be pretty much the same, if you can't find it in vista then post back here and I'll find one of my boxes that still has vista on it to tell you the exact procedure for it...
BTW sorry for all the left & right click crap, just used to explaining it that way to my father on the phone that way, otherwise he ends up on some damn page in internet explorer asking why I sent him there!?....