How to boot using usb

[6swans]

I would like to know if its possible to boot a pc using a external HD and a usb connection. I have an external HD with winxp home edition and it connects via usb. How do I use it to boot a pc with a p3,733mgh,384mbram,cd,floppy but no HD. I have tried bios booting from c,d,e,f,g,scsi and any combo my bios has. I know I could easily take HD and install inside machine but I want to see if its possible to boot from usb. Any help would be appreciated. Thanks

 

[Nodsu]

Yes, you can boot your PC from an USB device if your BIOS and the OS used support it. I have run DOS and NetBSD off a flash drive no problem.

No, Windows XP cannot boot or run from an USB drive because some fundamental OS design features.

 

[LNCPapa]

Using Bart's PEBuilder you can boot Windows XP with several tools included.
Take a look here http://www.nu2.nu/pebuilder/

Here's a decent write up on the entire process: http://www.tomshardware.com/2005/09/09/windows_in_your_pocket/

I doubt, however, that with a machine that old your bios will support booting via USB.