I have a Seagate hard drive and need to use it on PC for work and MacBook and Mac Desktop. The hard drive works on both the PC and Mac desktop but on my MacBook it only comes up as read only. How do I fix this?
You will need to format the drive with a filesystem that OS X and Windows are able to understand.
You haven't stated the size of the drive, but my suggestions would be exFAT, as it can read/write on both operating systems, and don't have the file-size limitations of FAT32, though you need to be using OS X 10.6 (Snow Leopard) or above.
Another possible solution is to purchase one of the two major NTFS drivers for Mac, thus giving your OS support for writing to NTFS drives without the need to format the drive.
Personally, I have gone with Tuxera's one as it allows installs on any macs you own and hasn't so far changed the version number (i.e. forced an upgrade cost) on me since I bought it back in around '09. I believe Paragon's one has been through 2 versions since then...