Most modern Linux distributions use ext2/3 filesystems for their partitions. You can download drivers for Windows
here or
here - both support both ext2 and ext3. (Though I think the second one is better, if you're using ext3.)
If however your Linux/Unix system is using something else (e.g. ext4, reiserFS, ...) you'll have to search - last time I checked, there were no fully functional drivers for ext4 available (though this is just a matter of time).
To check, what filesystem(s) you are using, enter the command
in a *nix console and it will tell you, which partitions are mounted with which filesystem.
Greetings,
Nepomuk