If you are confident that you can locate all of your sensitive data, you could leave Windows intact and use this free DoD type eraser
here (Download.com link)
Format operations can still leave data on the disk. A DOS based zero-writing program is highly recommended if you are re-installing the OS like
this one.
Conan offers excellent advice re: downloading your drivers and such from dell.com/support.
Interestingly, for secure deletion of data on hard disks on a project for the MoD, I had to use a screwdriver and a hammer. And no, you can't re-use the HD afterwards
We used electromagnets and drills - then the hammer.
