lots but they may/may not help.
the boxes left on the screen is one of the limitations/design flaw of winXP (and all OS's leading up to it)
Vista doesn't do this (its not supposed to anyway and I haven't seen it) - so installing vista would solve the problem (bit drastic thou)
Install the latest patches for windows, drivers for your video card, bios update your video card, bios update your motherboard.
this won't stop the problem occuring but it shouldn't occur as much.
the other thing that may help is more ram (no system specs so don't know what you have)