Hi, Boggins,
have you been able to boot the win 7 using usb. Your saying is natural, the pen drive does not have any thing like alert as cd dvd when we try to install. So, it is natural once it is chosen, it directly loads the windows, first by copying files thro white bar.
If you are able to boot with it ok. But the problem is i also tried what you have tried but it stops at 99 percent. Did you check the format of file imgburn burnt? what was the file. Even i tried to convert the imgburn udf iso to iso 9660 format, but on using windows tool, you get error exactly at the finishing stage..
But after so much trial and error, i found the method. Even i tried another tool and it says some other errors. First we have to create a partition on the pen drive to make it work.It is a simple process. If you have succeded in iso, then ok. Otherwise, i will give you a different method. It was success for me. I have been able to run the win 7 after trials from dvd. The dvd player is not at all at fault, but the error message is the wrong one. If you still has trouble, i will give the details.