I agree with gurm=="if" your system will boot from an usb source, then your system should do it "if" you have compatible equipment/drivers/software/etc.
I assume you are trying to boot from Linux on a disk or Win Lite or whatever? A quick partial diagnostic would be to see if your system would boot from your source disk when that disk is using a direct ide connection?
Also--does your system boot from a standard usb harddrive partition?
Maybe no answer there but might help you narrow down the issues.