I've purchased Oblivion whilst on offer on Steam and don't want to be logged into my parents' account. Is there a way I can run the game without Steam running also?
You can use offline mode so you don't have to sign in:
1. Tick the "remember password" checkbox in the login box
2. From the menu, choose "Steam" then "Go Offline" and click "Restart in Offline Mode"
3. Now you can run Oblivion without being logged into your parents' account, but Steam is still running (that shouldn't be a problem though)
Not that I know of, except for buying it before it came on Steam (which is impossible now) or getting a torrent, which is illegal.
Every Retail of Oblivion is non-steam. So are other digital destributioners. The only time Oblivion needs Steam is if you purchase it via Steam. It's not a Steamworks-game.
However, if you did, the only way you start it without Steam MIGHT be to start the .exe directly - no garatunee and never working with Steamworks-games (but as mentioned, Oblivion ain't one. Skyrim, however, is.)
Alternative is the already mentioned Offline-Mode.
1 - always login automaticly (means turn on that feature)
2 - Start the game once. You don't need to play it.
3 - Click on "Steam -> Go Offline" and start Steam in Offline Mode
4 - Play
And if it's just the account you're worried about - why didn't you make a new one entirely? Would have been way easier.