I wish I could recommend the Linksys USBBT100 Bluetooth USB adapter unconditionally, but I can't, because sometimes I have a hard time installing it on different PCs. There's something funky with the XP Bluetooth stack that makes it difficult to configure Bluetooth devices with certain hardware configurations.

It's only $43 now, so you could give it a shot and return it at Amazon if it doesn't work. Glancing over the user reviews, I see that many people got it working just fine.

Another idea is to check with Plantronics support. I say this is because I just took a look at the 520 user manual, and it makes no mention whatsoever of pairing the thing with anything besides cell phones. Plantronics sold a specific USB version of the Voyager 510 for VoIP calls, so the company is definitely familiar with the idea. But I'd like to hear them say, "Yes, it does work," before you spend money on a Bluetooth adapter for your PC, just to be on the safe side. (It should.) Maybe they'll have a recommendation too.

Sorry I couldn't give you a more definite answer, but hope this helps.

-Jamie