Someone was asking about this in microsoft.public.pocketpc a couple of
weeks ago, and the concensus seemed to be that there is no solution,
so I think you're SOL I'm afraid.
Here http://tinyurl.com/bxusq is a link to the thread.
The obvious workaround would be to not use WMP 10, unless you buy
DRM'd content there are plenty better media players out there. Or a
kludgy solution would be to use something like RtvReco
(http://www.rtvsoft.com/RtvReco.htm) to automatically "close" the
ActiveSync window every time it pops up, or even run a batch file to
kill AS completely. You'd have to remember to disable RtvReco when you
actually do want to see the ActiveSync window though.
C:\WINDOWS\$NtUninstallKB894476$\spuninst\spuninst.exe
KB894476 is the offending hotfix that makes this happen ...there is an uninstall for it within the folder in Windows directory that has this hotfix info ...look for it amongst the "blue" folders at the top of Windows that has that (I have XP).
look here: http://www.micrologics.co.uk/forums/viewtopic.php?p=34&sid=eb15e3a3b34f9b40a795e1265eeae5c3#34
look here: http://www.appdeploy.com/packages/detail.asp?id=518
I am not an expert so do it at your own risk ...I didn't see anything die yet. I dunno if it is good for anything but WindowsXP sp2 with ActiveSync4.1 and WMP 10 ...good luck!!