Having Trouble Booting Kali Linux Off Usb.

I herd about kali a wile a go and decided that i should install it. i followed a tutorial that used win32disk imager but when i tried booting off it it just booted windows normally. i tried this method multiple times on the same file but still the same thing. I then tried re-installing kali but still the same thing. I tried 2 other methods one doing it manually and the other using Universal-USB-Installer but still the same thing. i also tried installing it on 3 different networks but still nothing and installing kali more than 7 times. The only unusual things i found was that all the iso files where different sizes (some 2.74 and others 1.24) and that sometimes the download would just stop halfway through and say it was done. Another interesting thing was that sometimes Universal-USB-Installer would come up with an error that the "file is broken".