Yahoo messenger voice chat not working?

[OWNAGE]

My friend has a Dell laptop and has windows vista basic. He cant get any version of yahoo messenger (lowest it can support to newest 10.0 beta) to have voice chat work. His button is greyed out and I had him go thru perferences and select AUDIO AND VIDEO DEVICES and according to him it's not even listed. The Voice Call button on the 10.0 beta is greyed out on my box as it is his and even when he had 9.0 he couldnt receive calls or make em. He only has a headset and I just wanted to do the voice chatting. Why it wont let him take the call to where he can at least hear me is beyond me. He's uninstalled and re installed all versions and still no results. He's also tried running the call set up and cant detect no headset or mic. He has no mic but that's fine he's not gonna be doing the talking, just me as it beats typing so much. I know he SHOULD be at least able to hear me but wont let us do the voice chat. Any suggestions?? He can hear audio on his laptop from whether cd's or any website , you tube or whatever with no problem, it's just voice chat ONLY on yahoo messenger and with any versions on his end. I can voice chat with ppl on my list with no problem even those that have no mic as well.