also my other pen drives would fail the same way... (i.e. after writing the same image on it, the same way as I just had written the image in the other drive, it would not be bootable...)
(note, I changed the image writing software!!! and also the formatting software -- I only don't name it because I don't want to blame any software unjustly

NOW I have found testdisk and I'm very happy about it.
One of the pen drives had geometry problems, 125 instead of 255 and 62 instead of 64 (or 63), and even after fixing it, it had this non-matching problem.. and it was not bootable...
the other one seems to be bootable (according to testdisk analysis), however, instead of 64 it has 63 as a value for one of the geometric params... AND my machine(s) won't boot from it
my question is whether a flash drive which lost its ability to be bootable can ever be fixed to boot again?
thank you so much in advance
Peter