Maximum PC has the "how to" install 7 from a USB key. I will testify that if you do NOT follow the instructions carefully it doesn't work, but if you do, it does.
Installed it on an old many times repaired hPaq laptop, a V6000 CTO, slow Semperon, 2GB, 40GB, nVidia 6150 graphics, 4GB ReadyBoost stick. Clean install, fresh format.
The thing rocks. Dude. Firefox, Norton 2009, WMP, WHS connection, Java, all the eye candy works. CPU use is amazingly low, responsiveness excellent.
I'm impressed.
rr