[ddouglass]

When during (time of show) your shows is the computer locking up?

Have either of you tried adding a cooling pad under the laptops? These help them stay cooler.
Also, depending on how dirty or smokey the environment is where you play, they may be getting dirty inside which will contribute to heat.

When was the last time you both did the custom updates from Microsoft? They put out new ones every week and many do fix bugs in operating system. Since Windows 7 is still pretty new I am sure there are lots of bugs that need fixing.