The other solution is to plug one of the devices into a three prong outlet (grounded), and the other into a two prong outlet, using an adapter if you need it (ungrounded). Doesn't always work though.
You aren't defeating the ground, you are using a different ground than the ground the computer is using.
The adapter has a metal ring that grounds it to the screw in the faceplate of the outlet, instead of the wiring inside the outlet. They are commonly used for Audio, with no issue.
If, however, you think you can't take care of your equipment properly, there is a little piece of hardware for about 10-15$ at guitar center that will fix the issue.