Please Check your system Settings.
Open Power Settings under Control Panel -> All Controll Panel Items -> Power Options.
Click "Change plan settings".
You'll find "Change advaced power settings".
Search for "Swichtable Dynamic Graphics" in the "Power Options" dialog and change the "Global Settings", "On battery" and "Plugged in" to "Maximize performance"
Now both, HeavyLoad and other programs which have the same problem shoud work again.
Also make sure you have the latest drivers installed for your graphics cards.
The purpose of HeavyLoad is to put your system under stress to analyze its behaviour and to determine if it runs stable at this utilization.
HeavyLoad is not a benchmarking tool and will not evaluate on how well a system performs in comparison to similar setups.
Please also keep in mind that stress testing a system can always lead to crashes and bluescreens and because of that, important data should be saved before running the tests.
A few hints on telling if a test was successful: