may i suggest two things
1 - invest in a memory stick, that way you will not have to download it every time you re-install a game, just save it, or even a DVD R/RW(though you'll need a dvd burner) or an exterior hard drive.
2 - quest codes last resort, i know, and yes the are cheats and will need to be entered via the console, just ask. if you don't want them, don't ask.
Response to #1:
Or you could burn it onto a disc. That's what I did. It's also more cheaper, too.
And nice computer specs. I wish I had a comp like that.