Anyone can install a fresh copy of Windows via DVD and even using a flash drive is passé these days. If you're looking for a new way to get Windows up and running on your machine that doesn't involve these tried and true methods, you can always blow the dust off your forgotten Sony PSP and use it instead.
Image: Gerard Keenan
Firstly, to answer you question: No, this isn't the most practical way to install Windows. Essentially, the PSP acts as a glorified card reader for a Memory Stick Pro Duo. That said, it does collect plenty of style points and I'm sure it would impress friends and family who regularly ask you to reinstall their operating system.
Plus, it gets your PSP doing something other than rotting in a drawer somewhere.
The most complicated part of the process is correctly formatting and partitioning the Memory Stick Pro Duo so that it can be booted from. Otherwise, it comes down to configuring the PSP for USB mode, plugging the handheld console in and setting it as the primary boot device.
Windows Setup will take care of the rest, giving you time to field questions about why exactly you're using a PSP to install Windows.
How to reinstall Windows on your PC using a PSP [Instructables]