Looking for a Gaming Headset to use with my PC.
Also could use some advice on setting them up to use for Gameplay.

Grandson now playing "Left 4Dead", and wants full
online experience.

Plantronis Audio 355 from Best Buy

Purchased this set today, but isn't functioning properly, not sure why.
Still get sound from external speakers and
voice commands not entering gameplay.

I don't know a lot about headphones personally, but a friend swears by these from Razer - he says they are the best he's ever owned under $100. They are on sale at Newegg right now for $45 with promo code EMCKGJC53 (free shipping). The 5-egg rating indicates that users really like them.

Razer Orca

Looks awesome Drac,
the price a teriffic and I'm sure
he would be wowed by the green,
but we need a boom mike for online multi-player gaming.

I don't even know what that is, katbear! Hopefully someone who knows more than I do can help you out!

EDIT: So, I went and looked it up. DUH!! It's an attached microphone!

Maybe go to the Razer website and look under products/gaming audio and the offerings they have. Some look absolutely awesome - some even have absolutely awesome high prices! I liked the Razer Carcharias. I have a Razer Death Adder gaming mouse and absolutely love it.

RazerZone

I bought my grandson the Orcas for Christmas and he loves them, but of course not for online gaming because of the lack of mic. He uses them for his IPhone music, I also got him the little earbud ones from Razer, so costly but they do have a mic, also for the phone. Those I found on Ebay brand new for $10.00 less, no shipping added. He says the sound is great and they have little attachment things for use on other gaming machines. I think I would try the $79 ones, I think all Razer headphones sound great.

Of course, those USB Megalodons with the 7.1 Surround Sound look like the ones to HAVE! Just never mind the $150 price tag....

My next ones will definitely be Razer, not sure which yet, don't need a mic but want the sound. I now have two Sennheisers and one Sony, pretty good sound, Sony's are not as comfortable but they are foldup for taking along. Neither one is noise isolating and I really really need that.