With a little look around this forum you will see that I regularly recommend that all background programs and screen/power save options are disabled during video capture etc. These programs are a major cause of freezing programs and more often dropped frames as even on a fairly modern PC this takes up a large portion of the available resources.
If you do search around you will also see that I always recommend getting hold of a free downloadable program to stop all the background programs (power save and screen savers still need to be disabled manually though) called 'EndItAll2' that 'does exactly what it says on the tin'

. it is geting to be a bit old and therefore more difficault to find, so if you do have trouble PM me your e-mail address and I'll forward a copy on to you.
Mark.