turns out there's an officially supported way to turn that [Vista] 30 day evaluation period into 120 days.You can "re-arm" the trial period for another 30 days, and do so up to 3 times. Here's how it works


http://www.downloadsquad.com/2007/02/26/run-windows-vista-for-120-days-without-activation-key/

February 26, 2007 (Computerworld) -- A bug in Windows Vista's built-in antipiracy technology is telling some users that they need to reactivate the operating system after they install new device drivers or run newly installed software.

Microsoft Corp. quietly issued a patch designed to fix the flaw in its Software Protection Platform (SPP) technology late last month. Criticized by some when it was announced last fall, SPP is an updated and more aggressive version of the Windows Genuine Advantage antipiracy tools that Microsoft included with Windows XP. But because of the bug, SPP may suddenly demand that a copy of Vista be "activated" even though the user and/or the computer maker did so earlier.



http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9011858