Microsoft has begun reminding users who last year blocked the installation of Windows XP Service Pack 2 (SP2) that a deadline is fast approaching. On April 12, all blocking mechanisms will expire and Windows XP and XP SP1 systems will automatically download and update to SP2.

"The intent of this alert is to provide you with a reminder about the upcoming deadline around the date on which Automatic Update (AU) and Windows Update (WU) will deliver Windows XP SP2 regardless of the presence of the blocking mechanism," said Microsoft.

Prior to the release of Windows XP SP2, Microsoft offered up work-arounds and other tools companies could apply to keep the massive security update from installing on PCs with Automatic Update enabled. Although Microsoft repeatedly stressed that SP2 was "an essential security update," enterprises were leery of widespread adoption until they could thoroughly test it. Microsoft gave in, first setting a mid-December 2004, deadline, but then extending it to eight months from the August release of SP2 to Automatic Update.

The eight months are up as of April 12, 2005.

"Beginning 12 April 2005 this temporarily blocking mechanism will expire and systems with Automatic Update enabled or interactively download SP2 via Windows Update will begin receiving SP2," Microsoft added.

April 12 is also that month's regularly-scheduled security bulletin and patch disclosure day.