I have Windows 7, 64 bit but know not to trust BETA software. And if you downloaded that RTM you get a contact at MSFT to talk about it.
But my only idea (I do have Outlook of an older version, WMDC and such) is to head to the control panel, internet options, programs and use that to set Outlook as default.
If that fails it's You and MSFT to hammer it out.
I'll decline to discuss the problem I encountered with Mcafee or Norton or other suites "privacy protection" feature that interfered with this. Or how those can step in the middle of email sync.
I am running a Dell XPS 1340 with Windows 7 Ultimate 64 bit, Office 2010 64 bit and Windows Mobile Device Center 6.1 64 bit.
I can not sync my mobile phone running Windows mobile 6.5 to my Outlook 2010.
Outlook opens fine and is my default mail client.
When I open WMDC, I get a pop-up indicating that Outlook is not my default mail client.
WMDC then opens fully and says it syncs, but nothing is actually syncronized.
I have seen on other sites that this appears to be a known problem that Microsoft is so far ignoring!