Welcome to discussions Sateendra!
Personally I would have prefered to save as MPEG-4, to view on a PC-but I don't think that counts.When you look at the file in your PC does it look like a QT movie or it looks as a .DAT file? In case it doesn't have an extension, make a copy of it at your desktop and add the extension .mov manually.Otherwise, you can always try with the Get Info pane make it a QT movie directly from your Mac prior to exporting.
P.S. : I'd like to help further, but I'm now on iMovie6 and don't remember settings...