Copied files from Mac to Windows produce 2 copies with _. in file name

Hi, all.

When I copy files from my Mac to Windows (10.5.2/XP), I get two files for each file I copy. The smaller file has "._" as the first two characters in the file name. What is this strange and incredibly annoying behavior and can I turn it off? Do I need those little files in Windows, or in Mac later on (in other words can I delete them?). I have been tossing them out and my files seem to be okay but I'd really like to know what's going on.

I also have trouble saving attachments to Windows folders from Mail - it saves them okay but then gives me an error message every time telling me it couldn't save them. (but when I go look the files are there and ok). Any ideas?

Thanks!

Karin

 

A .DS_Store no-doubt.