First thing you want to do is go to your desktop then left click on your steam then click on properties
once you have done this then go on compatibility
next it should bring up this screen
click on "run this program as an administrator"
restart your steam right click on steam then click exit steam
then it should come up with a screen such as run as admin click "yes"
then it might come up with another window just click "cancel" then load up steam then your mass effect should work now enjoy :D

Note this works with:
mass effect 1 & 2