"The fixes largely centre [on] enhanced security, reliability and compatibility problems based on the code review that the entire Windows division did and will continue to do," said Greg Sullivan, Microsoft's lead product manager for Windows XP.
But central to the service pack is the way Microsoft has relaxed the terms of its contracts with PC manufacturers as part of its settlement of the US Department of Justice's antitrust case.
"When we signed the consent decree there was a list of eight things we promised to do, from properly documenting application protocol interfaces between the middleware and the internal Windows systems, to licensing protocols between clients and servers so third parties can license those from us and create compatible implementations. This is just one component of our larger compliance effort," Sullivan said.
When XCP was launched last year, Microsoft insisted on installation of its Internet Explorer Web browser, VM Java virtual machine, Outlook Express e-mail client and Media Player software.
Service Pack 1 will allow PC manufacturers to install third-party software to replace these components of Windows XP.
In spite of the change, Internet Explorer, the software at the root of the US Department of Justice's antitrust case against Microsoft, will still be part of the OS.
Neil Laver, Microsoft Windows XP product manager, said the new Service Pack would not affect the behaviour of XP Explorer or the Active Desktop, both of which use Internet Explorer to show Web content.
However, he said PC manufacturers would be able to preload Netscape. This would mean, for example, said Laver, "If you click on a link it will open Netscape [instead of Internet Explorer]."
Laver added that Internet Explorer would also be the underlying Web engine within the Windows HTML help system. The browser window within MS Word will also be based on Internet Explorer.
Some analysts believe that the changes may not be enough to open up significant new area of opportunity for competitors.
"I think some of these changes accomplish what was asked of them. But am I convinced that it puts Microsoft's products on an equal footing with those of others? I think they still have an advantage," said Al Gillen, research director for IDC's System Software group.
Graham Fisher, of analysts' group Bloor Research, said that the high level of integration between Windows and Internet Explorer meant users might find an alternative browser more trouble than it is worth.
"If people take a choice and start using Netscape they have to accept there will be extra maintenance involved."
Since Internet Explorer is still running behind the scenes in Windows XP, he said users might find they still need to update Internet Explorer patches along with any updates they would need to apply to the alternative Web browser they choose to install.