I have a Sony Vaio laptop with inbuilt "Motion Eye" video camera. It works
fine with the Sony camera capture software but Windows Live Messenger seems
to cause problems.

When I start Messenger, the camera usually works fine but if I completely
exit Messenger (closing the notifications area icon too) and then start it
back up, it just says "This camera is in use by another program". If I then
go into the Sony camera capture software, it tells me the same.

It seems that only Windows Live Messenger causes this problem as I have open
and closed the Sony Camera Capture software many times without problems.