How can I read/write to several hard drives created on windows 7,8 from OS X
The "read only" status has to do with the UUID of the files on the drive no longer matching what is coming from your Mac.  So, basically, you have to "orphan" those files.

Here is a good writeup on how to do it, but note that this is an UNOFFICIAL method and not sanctioned by Apple.

How to Enable NTFS Write Support in Mac OS X