Access Macintosh HD while booted from Windows 7 on Bootcamp Partition?

Whenever I try to access files from my Macintosh HD partition while booted from Windows 7 in Bootcamp, I always get permissions errors. I don't have permission to access or change any of these files. I can open the files, I just cannot write to anything or save anything on the mac partition from windows.

Also I cannot write to some of the external drives I use for storage because of permissions as well.

What can I do?