Hi and welcome to Discussions,
Mac OSX can read and write from/to Windows partitions that use the FAT32 file system (called MS-DOS in OSX Disk Utility).
Mac OSX can only read from partitions that are using the NTFS file system.
For write access you have to use third-party helper like NTFS-3G
http://macntfs-3g.blogspot.com/ or Paragons NTFS for Mac
http://www.paragon-software.com/home/ntfs-mac/
Apples BootCamp Drivers version 3.0 and above include read access from Windows on Mac OSX partitions, but personally I find this feature at the moment merely "experimental".
For full read and write access from Windows on OSX partitions, MacDrive
http://www.mediafour.com/products/macdrive/ is the only solution.
regards
Stefan