Microsoft Tuesday began offering Windows XP SP3 on its automatic download Web sites and resumed automatic downloads of Vista SP1 after compatibility issues arose last week.The company said both service packs are now available via Windows Update and the Microsoft Download Center.

The release had been delayed after Microsoft discovered an incompatibility between both XP SP3 and Vista SP1, and Microsoft Dynamic Retail Management Software, specialized software for retailers. In announcing the release of SP3 for XP, Microsoft said it had addressed this problem by deploying a Windows Update filter that would keep the service packs from being offered to customers who use Microsoft Dynamics RMS, and advised these users to contact Microsoft's support services for more information.

The company posted a 316MB stand-alone installer on its download site and recommended it to users updating multiple machines. An even larger .iso, or disk image, file has also been added to Microsoft's Download Center; the disk image tipped the scales at 545MB.

Microsoft has also resumed automatic distribution of Vista SP1, which was suspended following discovery of the RMS incompatibility.

Overview of the new features delivered through SP3:

- Network Access Protection (NAP) to help organizations that use Windows XP to take advantage of new features in Windows Server 2008

- Improvements to black hole router detection (detecting routers that are silently discarding packets)

- The Security Options control panel in Windows XP SP3 now has more descriptive text to explain settings and prevent incorrect settings configuration

- In System Center Essentials for Windows XP SP3, Administrator and Service entries will be present by default on any new instance of policy

- Microsoft Kernel Mode Cryptographic Module, which is a FIPS 140-1 Level 1?compliant, general purpose, software-based, cryptographic module in the kernel mode level of the Windows operating system

- Windows Product Activation: As in Windows Server 2003 SP2 and Windows Vista, users can now complete operating system installation without providing a product key during a full, integrated installation of Windows XP SP3