I guess one thing that Dells have going for them (sometimes it seems like it's the only thing going for them) is the disk they supply with new computers is a copy of the MS Operating System disk with nothing added but a small OEM section that passes pre-activation when it sees the correct BIOS boot flag. For Vista, the install.wim file on a Dell reinstallation disk is the same as on an OEM disk, allowing users to do clean installs of just Windows if they wish.
They also create a factory image of the OS and all of the software purchased with the computer (as well as the crapware) and stash that in a recovery partition for automated restoration to factory-shipped conditions. In practice, I think the factory restoration process is used more by Dell tech support than consumers. In 10 minutes they can have you back to square one, a known quantity, and then proceed with real troubleshooting..... of course, at the expense of losing all data not backed-up.