USB Hard Drive... Read-Only?

I have several USB hard drives I have connected to my Intel Mac, and they are all listed as "Read Only." I want to be able to use them both on PCs and my Mac's (both Intel). I am curious as to what I need to do in order to achieve this. Is there a piece of software that will allow this? Or is there a piece of software that will aide me in the process of getting to a point where this can be achieved?

Thanks all!

If they are formatted as NTFS you will only be able to have read only access on your Mac. They will have to be formatted as FAT32 to be used for both read and write access across platforms.

Alright... Is there a good way to go about this? Is there software that can aide in this?