The Elder Scrolls V: Skyrim is now available to pre-load on Steam and Direct2Drive, letting you grab 99% of the files needed to run Skyrim. That should be about 6 gigabytes according to the system specs . Then the vital de-encryption data that will turn these files into Tamriel will be shunted to everyone at launch on Friday. Then the game will unlock and we'll all be able to finally play it ... almost.
Once Skyrim is decrypted, you'll then have to wait for another download before playing. Bethesda say that "All platforms going to 1.1 by 11/11/11" with a day one patch that "fixes some minor stability and quest progression issues." Skyrim's going to have a pretty huge world map, and there's bound to still be a few bugs lurking in there somewhere. Oblivion and Fallout 3 had problems with AI getting stuck in doors, objects floating mysteriously and other bizarre anomolies. It wouldn't be a Bethesda launch without a few of those hitting YouTube.