Image compressor

[bowers01 +]

Hi,
I have had a few people email me latly saying that their photos wont upload.
Turns out they have a 5mb picture and are on a slow adsl connection, rather than limit the file size because it works fine with people on a good connection i have left it but want to set up a help page.
Does anyone know of a free image compression utility(mainly for windows but bonus for mac) that users can just download and select the image they want and it just overrights it or puts it in a new directory?
I know infran view is good but novice users cant figure out how to use it. My site is for truck and machinery operators, most of them dont know how to turn a computer on.
Cheers,
Nick