Windows XP has been released quite a while ago (RTM: August 2001, GA: October 2001) and most people are anxiously waiting for Windows Vista (Estimated RTM: November 2006, Estimated GA: January 2007). Two million are expected to download the Windows Vista Beta 2, which should become available before the end of this quarter.

However, there are a number of free downloads from Microsoft to improve Windows XP. Some of them are in beta versions at this point, but I have found even those to be quite stable in the pre-release format.

Here a few of my favorites by Category:

Updates and Security

What: Windows XP Service Pack 2
Link: http://www.microsoft.com/windowsxp/sp2
When: August 2004
Summary: This is the latest Service Pack for Windows XP. The usual bug fixes are there, but a lot of security features are in the pack.
Windows Vista: Many additional security improvements that cannot be backported to XP are there, including User Account Control and Improved Services Hardening.

What: Microsoft Update
Link: http://update.microsoft.com/microsoftupdate
When: June 2005
Summary: Unlike the old Windows Update, Microsoft Update automatically downloads and install updates for other Microsoft applications, like Office.
Windows Vista: Microsoft update is built in and ready to go. All the work a Windows XP user has to undergo on the first download of Microsoft Update is avoided.

What: Windows Defender Beta 2
Link: http://www.microsoft.com/defender
When: Beta 2 released on February 2006
Summary: This is Microsoft's new anti-spyware software.
Windows Vista: Windows Defender is built in and ready to go. The Security Center checks for it being enabled and up-to-date, the same way Windows XP SP2 checks for the firewall being enabled.

Productivity

What: Internet Explorer 7 Beta 2 Preview
Link: http://www.microsoft.com/windows/ie/ie7
When: Latest Beta 2 Preview on March 2006
Summary: The next browser from Microsoft including a number of new features (new navigation buttons, tabs, search, RSS support, improved printing, among others) and improved security (phishing filter, better add-on handling, improved certificate support, delete browsing history, among others).
Windows Vista: IE7 is built in and security is further improved, with the new IE7 Protected Mode.

Windows Desktop Search (Windows Live Search Toolbar Beta)
http://ideas.live.com

ActiveSync 4.1
http://www.microsoft.com/windowsmobile/downloads/activesync41.mspx

Multimedia

Windows Media Player 10
http://www.microsoft.com/mediaplayer

Windows Movie Maker 2
http://www.microsoft.com/moviemaker

Photo Story 3
http://www.microsoft.com/photostory

Development

.NET Framework 2.0
http://msdn.microsoft.com/netframework/downloads/updates/

WinFX Beta
http://msdn.microsoft.com/winfx/

There are a number of unique features of Windows Vista that will never work on Windows XP, but if you want something to play right now, the links above will keep you busy until the public beta 2 comes out.