Linux can do that, but be sure you are not attempting to install Windows XP to some USB drive since I've never seen this work.
Bob
Wanting to use external usb HDD for notebook, delete partitions and format went ok, now do not know how to load oper sys to disk from notebook drive. Go "My Comp" and select drive, no options there. Right click, select "Manage", go "Disk Manag", only gives Format and Delet Part again. Should I try switching to Boot USB first with Oper disk in tray? Only thing I know is swap HDD's and load external then switch back. Running Gateway lap w/XP-Home, 2.6 AMD 64 chip w/1-gig memory, and both HDD's @ 100-gig. Want external to run my XP-Pro, but will take Home if nothing else. Oh, Gate restore was no help, just wants to load on existing drive and XP-Pro is not decerning internal or external so I esc out. Please help a newbie, the newbie you save may be related.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic