Pre-orders for Windows Phone 7 handsets in some European markets have already sold out, according to some news reports. The issue seems to be the collision of high consumer interest with small inventories, at least of some of the new phones.

Orange, T-Mobile, and O2 earlier this month launched their pre-order pages on their U.K. websites, for the HTC 7 Mozart, HTC HD7, and Samsung Omnia 7 (not all carriers are offering all three phones). Two other carriers, Vodafone and Three, will also be offering phones: LG Optimus 7 and HTC 7 Trophy.

But demand has been so heavy that Orange, for example, now shows an "out of stock" alert on its Web page for the HTC 7 Mozart. In response, the carrier has now started offering vouchers, worth about $32 to customers that want to order the sold-out phones

There doesn't seem to be official word of what's constraining supplies, or how constrained supplies are. There's plenty of speculation. The Register's Bill Ray reiterates a couple of the rumors: Samsung is short on the high-resolution AMOLED screens for the Omnia 7, and HTC "seems to be having [unidentified] software problems" with its Windows Phone 7 models. 

A U.K. news site, Mobile Today, apparently was the first to report on the stock shortages, quoting an Orange email to retail managers, warning that "we will be launching with limited amounts of both our Windows Phone 7 devices, the HTC 7 Mozart and the Samsung Omnia 7. We are, however, anticipating that our competitors could be in a similar situation."

HTC HD7 Windows Phone 7

If the shortages are severe or prolonged, it could be a major blow to Microsoft. Since Windows Phone 7 was unveiled in February 2010, Microsoft has said phones with the innovative OS would be available for the 2010 "holidays." The company has a lot riding on the new OS, which directly competes with Apple iOS and Google Android for consumer smartphone dollars.

Shortages will be a blow to Microsoft's carrier partners, which overall seem to be investing heavily in promoting the new phones. In the U.K., Orange will offer a set of new Orange services pre-installed on the Windows Phone 7 devices. Among them are a movie ticket app, which among other things lets you redeem a voucher for a movie ticket; Orange Maps, offering turn-by-turn GPS directions; Your Orange, for managing your account; and Orange Daily, a selection of concise news, sports, and weather information.

In the U.S., GSM carriers AT&T Wireless and T-Mobile will offer Windows Phone 7 handsets, starting Nov. 8. CDMA models are due out for other carriers, presumably Verizon Wireless, in the first half of 2011.

John Cox covers wireless networking and mobile computing for Network World.