I have 80 computers to do on
It shouldn't take as much as a minute on each of the computers. Even
allowing for walking from computer to computer, its probably no more
than and hour and a half or so in total.
If I were you, I would put any .bmp file on a thumb drive or CD, then
take it to each of the 80 computers and do what I said below 80 times.
It's likely to be much faster than the time you would spend looking
for another way, trying it, finding out that it didn't work the way
you thought it would, fixing the problems that resulted, etc.