Converting a pair of trousers into a laptop sleeve

I ordered one of the new metal Macbooks on the night they came out. So far it's been a great machine, but there has been one minor problem - it's a different size to my old 12" Powerbook. So obviously my old crumpler laptop case was going to be no use.

After purchasing some green cotton thread, grabbing an old pair of trousers and a couple of hours sewing (by hand) I ended up with a perfectly workable laptop sleeve for my Macbook: