Although Microsoft said it made the change to simplify the work in tracking licensing rights for PCs, the continued popularity of Windows XP may have had something to do with it. At the Worldwide Partner Conference (WPC), which opened Monday in Washington D.C., a company executive acknowledged that 74% of business computers still run XP.
The downgrade rights are available only from OEM copies of Windows 7, those that are pre-installed by computer makers.
"Going forward, businesses can continue to purchase new PCs and utilize end-user downgrade rights to Windows XP or Windows Vista until they are ready to use Windows 7," LeBlanc added in his blog post.
The change impacts only consumers and businesses that don't subscribe to Software Assurance (SA) -- Microsoft's annuity-like upgrade guarantee program -- or those who purchase Windows through volume-licensing plans. Those companies already had downgrade rights from any edition, including Windows 7, to any previous version going as far back as Windows 95.
Other deadlines that Microsoft had previously scheduled for Windows remain in place. Computer manufacturers must stop installing Windows XP Home on netbooks as of Oct. 22, 2010, and they may sell PCs with Vista pre-installed only through Oct. 22, 2011.
Computer makers are also slated to stop offering factory-installs of XP Professional downgrades on PCs with Windows 7 Professional licenses after Oct. 22, 2010. That means Windows users who want to downgrade a Windows 7 system to XP must do it themselves starting Oct. 23 of this year.
It's unlikely that many Microsoft customers, even the largest corporations, will downgrade to XP as long as Microsoft allows. That's because the nearly-nine-year-old operating system falls off the support list for good in April 2014.
On Tuesday, Microsoft will supply the last-ever updates for Windows XP Service Pack 2 (SP2), the 2004 upgrade that was superseded four years later by XP SP3.
However, some computer makers continue to sell new PCs with a factory-installed downgrade to Windows XP. Dell , for example, offers downgrades on some Latitude notebooks.
The practice was much more widespread when Microsoft marketed Windows Vista. Then, customers clamored for ways to return to XP after buying new PCs equipped with Vista, a rebellion that forced Microsoft to delay several times the end of XP availability to both large and smaller computer sellers.