I am unable to reproduce this issue, however I suspect that you installed Origin on your main drive and by default it is trying to install Mass Effect 2 into the 'Downloaded Games' folder configured within your Origin settings?
When I attempt to install Mass Effect 2 via Origin (I don't have it installed via Origin as I originally purchased it on Steam, but I have added my CD key to Origin for the purpose of testing this for you) I get prompted simply for the language I wish to install the game with and then asked if I want to continue after being prompted with the disc space check;
Once I've accepted the end-user license agreement, and the download has started, files begin to appear in the 'games\Mass Effect 2' subfolder inside my Origin installation directory;
Therefore I suspect that you ensure that the configuration settings for Origin have been set up to ensure that both the 'Downloaded Games' and 'Select where you want to store your game installers' settings within the Origin settings page are configured to point to the hard disc that you intend to install Mass Effect 2 on. I personally chose to use a 'games' folder inside of my Origin installation folder to follow the way that Steam does things but you can customise this to your own liking.