Hi,
Please confirm how did you enable boot in bios menu. What is the menu you selected. If it is supported in bios, then there is nothing wrong if it is booted from the pen drive. It should work.
One last suggestion. Pl download plbt.iso. Download the iso to a disc, cd, by burning the iso file using imgburn.
Then you select the boot priority to cd dvd . Then it will auto boot from cd and will give options in your screen the boot choices. You select Pen drive , move the cursor down and then enter in Pendrive option.from it. It should work. Otherwise pl report.
I am enclosing this iso here. Please download and then try to burn it using nero or imgburn. Then report back