I bought this BT Agile USB Corded Internet Phone to use as a microphone with NaturallySpeaking voice recognition software (the NaturallySpeaking version I have is Dragon NaturallySpeaking Preferred 10.0, Education Version).
I plugged this handset it into (a USB port) on my laptop (running Vista Home Premium 32bit) and Vista recognised the handset immediately (i.e. without the need to look on the internet for any drivers - incidentally, there is no driver disk in the box).
The NaturallySpeaking software also recognised the handset immediately and it passed all microphone/sound quality tests that NaturallySpeaking requires a microphone to pass.
I took a bit of a risk with buying this as I wasn't sure, given the price, that it would be good enough quality to use as a microphone for Dragon NaturallySpeaking - in my experience NaturallySpeaking can be a little picky about microphone quality. However, given the cost saving of this compared to some of the other microphones for use with NaturallySpeaking, I am very pleased that I took the risk as it works very well for my purposes.
I haven't tried using this handset as a VOIP phone connected to my laptop (as I have a Skype app on my mobile phone, so I have no need for that aspect of it).