File Permissions

I have windows partitions, and I want to move some of my work to them so
I can access the files in Windows. When I try as a user or as root, it
won't let me copy anything to the windows part of my hard drives...
I have tried chown on them and chmod, but it won't allow me to change
them... It allows me to write to the partitions as root, but doesn't
allow me to copy files to it? What am I doing wrong?

Thanks,

Eric