Installing XP from a USB Drive

[Drtigerlilly]

I want to know how i'd go about installing XP from a boot drive, i've used nlite to copy the windows installation to my hardrive & have slipstreamed with sp2 but don't want to burn a cd, my external usb drive appears in the boot menu, but i'm not sure how to direct the computer, dos i'd assume to the folder where i have the windows installation to start the setup.

I'm going to need full out instructions, whereas i'm not a newbie in the realm of these things, anything dos related & i'm out. I was told something about doing an autoexec.bat file...don't remember if i got that right HELP!!!