New upgrade round, in two phases, coming up:
Phase 1. – For those who still aren’t using Windows Live Messenger 8.5 (Windows XP and Vista, optional upgrade):
First, everyone running Windows XP or Windows Vista will get a prompt encouraging you to upgrade. When you accept the upgrade, the new unified installer will launch and start upgrading Messenger. While it’s installing, you’ll have the option to download and install other Windows Live applications. You don’t have to take any of them, but we think you’ll like them and hope you’ll give them a try.
It will take a couple of weeks for us to get this upgrade out to all users, so if you don’t get it right away don’t worry, it’s coming. If you don’t want to wait, you can go to http://get.live.com/messenger/overview to download and install Messenger 8.5 right now.
Phase 2. – If you are still using a Beta version of Windows Live Messenger 8.5 (forced upgrade):
After everyone’s gotten the optional upgrade, those of you still running a beta version of Messenger 8.5 will receive a required upgrade to the final version. When this phase kicks in you’ll be blocked from logging in until you complete the upgrade…
A special note for those of you running Messenger 8.5 Beta on Windows XP 64-bit or Windows 2003 Server
The final version of Messenger 8.5 will not install or run on your OS. We don’t want you to get stuck out in the cold so you will not receive the mandatory upgrade to the final version. However, these operating systems won’t be supported by future Messenger versions. You may stay on your current beta version, or to get to a more stable final version we recommend that you uninstall Messenger 8.5 and go back to Messenger 8.1.
Update on the note for Windows XP 64-bit and Windows 2003 server:
Messenger 8.5 itself works fine on these operating systems, it is the new Live installer that does not. Thanks to Jonathan Kay for notifying me, more info can be found in his article: Attention Messenger team: Messenger 8.5 works on Windows Server/Windows XP x64 + petition