[Update 11/12/09: Well, that didn't take long. Though Microsoft may not have known yesterday, Hard Drive Transfer Kits are back in stock today! As in, right now. So, if you need one, or had been told to "use your own hard drive" you may want to give 'em a call at 1-800-4MY-XBOX and get yourself squared away.]
If the recent price drop has encouraged you to hedge your bets and replace your aging, bound-to-die Xbox 360 with a quiet, new, Jasper-equipped 120GB Elite, you'll want to pay attention. As relayed to us by tipster Paolo, and confirmed by a Microsoft representative, the Hard Drive Transfer Kit – which is currently available for eligible consumers by calling 1-800-4MY-XBOX – is "out of stock at the moment" and the company does "not know when inventories will be restored."
Of course, it's "working on resolving this shortage as quickly as possible" but in the interim, if you want to get data of your old 'box and you didn't buy the 120GB drive at retail (which comes with the HDD transfer kit) Microsoft Support recommends that you "use your old hard drive." Not the most elegant solution, especially if you're trying to unload that old Xbox. We've asked Microsoft to clarify when we might expect the Kits to be restocked and we'll share with you if and when we hear back.