Why did Microsoft delay rolling out XP SP3 for a week?

The company said it had only recently discovered a compatibility bug in the retail point-of-sale software it sells to businesses that cropped up in XP SP3 (and also the newest version of Windows Vista, SP1). As a result, it postponed the expected April 29 release date.

According to a message posted to the support forum for Microsoft Dynamics Retail Management System (RMS) on April 24, the company had identified problems, including data loss and corruption, when the software was run in Vista SP1. Only after it announced XP SP3's delay, however, did Microsoft confirm that the same bug affected RMS when it was installed on a PC running XP SP3.

Once Microsoft had created and deployed filters to WU so that machines running RMS would not be offered the XP SP3 update, it cranked up delivery.

What's new in XP SP3?

As we've said before, not much. It does include a few new features, however, which are spelled out in this overview. The biggest change, at least in terms of the number of users it will impact, is the modification to product activation. New installations of Windows XP SP3 will give users the same 30-day grace period currently offered to Vista customers before they're required to enter a product activation key.

The change is only for new installations and doesn't come into play if you upgrade from SP2 or an even earlier edition of XP. If you're just updating, you shouldn't be asked for a product key.

What's been fixed in XP SP3?

Lots, according to the official list that Microsoft published. The list, which you can view here is long. By our count, the service pack contains 1,174 individual patches and hotfixes, essentially every one that Microsoft's issued since it rolled out XP SP2 in 2004.

And the list is remarkably up-to-date. For example, the most recent security patch that applies to Windows XP -- MS08-025, a fix for a flaw in the kernel that was issued April 8 -- is included.

What if I have problems upgrading to SP3?

Normally, Microsoft refers users who obtained XP as part of a new PC to the computer manufacturer or reseller when problems pop up, or charges US$59 per support request to answer questions. But as is its practice with service packs, Microsoft will provide free support for any XP SP3 installation or compatibility issue. You can reach support free-of-charge by telephone, e-mail or real-time chat.

The place to start is this XP SP3-specific page on Microsoft's Help and Support site.

Will XP SP3 be available at retail?

Nope. Microsoft confirmed today that XP SP3 will not be shrink-wrapped for store shelves. "Windows XP SP3 is available to OEMs as an option for some of their product lines [and] for Volume License customers to simplify maintenance of their Windows XP machines," a company spokeswoman said after noting that others won't see SP3 as a separate product.

That means you'll have to do an after-the-fact update to SP3 on any newly-purchased-and-installed copy of Windows XP.