Navod jak dat Win7 na USB disk napr. http://www.intowindows.com/how-to-install-windows- 7-to-usb-external-hard-drive-must-read/
najdene googlom.
P.S. ak tam chces dat WinXP tak uprava instalacky popisana napr. tu http://www.mp3car.com/winnt-based/125408-install-w indows-xp-on-a-usb-flash-drive.html pozor mozu byt v kode neziaduce medzery ktore tam pridal web