The company said both service packs are now available via Windows Update and the Microsoft Download Center.
Last week, XP SP3 and Vista SP1 were held back after Microsoft admitted to compatibility issues between the operating system software and Microsoft Dynamics Retail Management System (RMS), a point-of-sale and store management software designed for small and midsize businesses. RMS is deployed by a small subset of XP and Vista users but Microsoft blocked access for everyone to the service packs.
Tuesday, the company said it had added a filter to the download sites to block the service packs from RMS users only.
A permanent fix is in beta and should be available in May, the company said in a statement to media outlets.
XP SP3 includes all the previously released updates for Windows XP, including security updates, and is for X86 machines only.
Windows XP was given a reprieve late last year when Microsoft extended its availability date to June 30, 2008. The software, which was the XP SP2 version that included security improvements, was originally slated to be taken out of OEM and retail channels on Jan. 30, 2008.
Microsoft reiterated in April that it would not extend the Windows XP deadline a second time and that June 30 remains the cutoff date.
Microsoft extended the deadline after customers complained that they were not willing or ready to migrate to Vista.
Mainstream support for XP, however, does not end until April 2009. Extended support, which provides free security updates, runs until April 2014.
In its final release, XP SP3 will be supported as a guest operating system on Microsoft's Hyper-V virtualization technology, which is slated to ship in the fall.
Microsoft last month released the first feature-complete beta of Hyper-V, which is an add-on to Windows Server 2008.