You do NOT want to write to a NTFS partition in Linux. You CAN do it, but it's buggy and it will eventually mess up your partition. Windows hates it too. I would suggest that you shrink the NTFS partition and create a FAT32 partition if you want both Windows and Linux to be able to read/write it. You can do this with gparted, qtparted, cfdisk, or parted/fdisk(if you are feeling adventurous). Gparted even has a live CD that you can download, burn to CD and reboot into to change the partition table.
chown doesn't have the 775 numbers, but chmod does. The number stand for the three different types of people / groups that can access that data. The three are: User (this is the account of the person who created / downloaded the file if the owner hasn't been changed), Group (the people in a group - such as users - that may access the data), and Other (everyone that isn't the owner or in the owner's group).
When you specify permissions as numbers (ex. 775) You are using a system in which read access, write access, and execute access are weighted differently. Read is given a value of 4, write a value of 2 and execute a value of 1. These numbers are added together to give you a number between 1 and 7, and (you guessed it) the sequence of three numbers relates to the User, Group and Other we spoke about earlier. So, the 775 from earlier can be broken down like this:
U = 7 = 4+2+1 = rxw (or read, write, execute)
G = 7 = 4+2+1 = rwx (or read, write, execute)
O = 5 = 4+1 = rw (or read, execute)
A better explanation of this can be found here: http://seanic.net/support/permission.htm
(the part at the bottom is what you want)