Q: The ones that came with my desktop, and even new ones I just purchased, don't work fully. The only speaker that works is the speaker with the power switch on it. 10 points to the first answer that helps.
A: Go to your sound options in the control panel and check that it's not in mono sound or that it's balanced to favour one side. If that's not the case then it's hardware related, is there a power cord leading into the other speaker? from either the other speaker or the powerboard?