Cheapest place to buy Windows software?

[Mockery]

So I finally settled on a new mini Netbook and just purchased it. Only drawback is that it comes with the Starter Edition of Windows 7, which is basically like a crippled version of the software. So I'd like to upgrade to a full version of it.

Since I haven't purchased a new OS in a while, I wanted to know if you guys have recommendations for where the cheapest place to buy a full version of Windows 7 Home Premium edition would be.

I know I could just download the upgrade on the netbook, but I'd prefer to have it backed up on disc with a full version.

Oh, and in case you're wondering about which Netbook I settled on (since I asked you guys for some feedback), I went with the Toshiba NB305-N410BL. Tested out a bunch o' netbooks and really loved this one. It had the most comfortable keyboard by far, a large touchpad, was in the right price range, etc etc. Purchased a 2 gig ram upgrade for it as well. Hooray :O