If you download and install using the EA download manager, the download manager may (or may not) start up every time you play the game. It won't affect anything if you're offline though. There is a way of trying to avoid the download manager starting up, though it may not work. Out of the 9 games I have installed in the way below (including The Saboteur and Mass Effect) only Medal of Honor Airborne is annoying enough to need the EADM to start up with it.
What you should do (and what I'll do since I can use my serial to download using the EA download manager, and it's faster) is:
- download ME2 using the EA download manager
- once it's done that, it won't automatically install. It will display text saying "install"
- navigate to folder the game files have been downloaded to, usually a folder in C:\ProgramData\Electronic Arts\EA Core\cache\
- close the EA download manager and use the EA setup file in the above folder to install ME2. You may have to paste the serial number EA emailed to you, as the EA download manager automates this process and puts the serial in for you.
- let the game install, activate and start up. It shouldn't require the EADM to start up with it, though you will have the option to start the game from the EADM. It will appear in your Windows Games Explorer list like any other game.
If anything goes wrong, you will still have the option to install ME2 from the EADM, as long as you haven't deleted the contents of the download folder or used the option in EADM to clear cache. But after you've checked your install is a success you will want to think about backing up the files or deleting them from your PC, as they and the eventual install will take up 14GB (28 GB if you count the downloaded files)!!!!