Windows Phone 7, Microsoft's latest foray into the mobile space, is now available to all in the US. The company's primary partner is AT&T, and they have the Samsung Focus  and HTC Surround (see our HTC Surround review and photo gallery) for $199 with a 2 years contract, with the LG Quantum launching in a few days. The phones are also available without a contract for $499. Meanwhile,  T-Mobile has the HTC HD7 for $199, with the Dell Venue coming in later this year. Microsoft has stated that they will put $400 million towards advertising Windows Phone 7 as they hope to compete with the iPhone and Android phones this holiday season. Gartner predicts the company's share of the mobile space will climb above 5% by next year.