yes it will, i know 3 people that use win 7 and winmx,
if you do get a problem, here's 1 thing you can do,
1, close down winmx
2, right click its icon, chose 'Properties'
3, click on the 'Compatibility' tab
4, tick the small box 'Run as' and chose in the drop down menu 'Windows XP'
5. click apply/ok
start your winmx and it should run without problems.