Microsoft made it official on April 3: There will be no new reprieves for Windows XP (other than on Ultra Low-Cost PCs).

Some customers and partners had been hoping the company might extend again the deadline for all PC makers to be allowed to preload Windows XP, rather than Windows Vista, on new PCs. But today, Microsoft officials said the current June 30, 2008 cut-off date would remain in place for the vast majority of machines.

The one new exception, as some were anticipating, are Ultra Low-Cost PCs (ULPCs), which Microsoft defines as systems like the Asus Eee and Intel Classmate — “significantly more restricted hardware with less expensive processors and more limited graphics capabilities. ULPCs should not be confused with the higher-priced and more robust UMPCs, or Ultra-Mobile PCs (a k a “Origami” devices); Microsoft is continuing to encourage UMPC makers to build their systems around Vista.

As Microsoft officials announced on April 3, makers of ULPCs will be allowed to continue to preload XP on ULPC machines until June 30, 2010, or one year after general availability of the next version of Windows, whichever comes first later (sorry, my error), according to Microsoft.

(Microsoft has said that its target delivery date for Windows 7, the next version of Windows, is some time in 2010.)

The majority of, if not all, ULPCs are incapable of running Vista, with its higher RAM and graphics requirements. But they can and do run Linux. That proved to be a good incentive for Microsoft extending the XP cut-off deadline for those low-end machines.

For plain-vanilla PCs, Microsoft is holding fast to its June 30 preload cut-off for XP. (In September, Microsoft granted PC makers a five-month extension, allowing them to continue preloading and selling at retail Windows XP until June 30 of this year. ) As Microsoft noted previously, users still will be able to get XP preloaded on new machines from white-box vendors/system builders through January 31, 2009. And Vista Business and Ultimate customers with volume-license contracts can still get XP via their “downgrade” rights.

Microsoft will still provide mainstream (free) support for XP until April 2009. Extended support (free for security fixes and paid for other help) ends in 2014.