After installing the Windows 7 RC, I installed the latest Windows Live Messenger.
There is a way around this however… you need to set it to run in Compatibility Mode for Windows Vista.
To do this, first exit Messenger, then locate msnmsgr.exe (in your Program Files directory) Right click it, select Properties
Choose the Compatibility tab, and select Windows Vista.
Hit ok, and then restart Live Messenger.
It now runs in the notification area!