As I have mentioned before, most if not all recent computers build in past 6-7 years have the option to force boot a device. Try finding that key by using google or by pressing different keys (f1-12 or del or end) and see if it gives you the option to boot from USB. This is typically the easiest way to see if your computer knows the drive is there. Dont forget to make sure USB legacy is enabled...as could fix the problem.
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~Just StopSpazzing~
Visit the UBCD Wiki:
http://wiki.ultimatebootcd.comPlease check your
UBCD ISO
MD5 Hash Sum; May prevent issues later on by not having an exact copy.
Currently Working on
Common Issues and Repair Tips on the Wiki.