2 computers ...2 resolutions

I have two computers . Both are set up the same . Yet on one , any photos
are a lot bigger files than the other. I visited a site with free textures &
photos this morning. On one computer a file was around 45,000 bytes. On the
other computer , the same file was around 145,000 bytes. I can't figure out
why they are different. Any ideas ?
Craig Flory