I have an external hard drive that I'm trying to copy all of my files from my iMac onto so I can transfer it to my PC, but it only gives me the option to copy what's already on it to my iMac and I'm trying to put files *onto* the external hard drive. When I right click on the hard drive, there's no option to paste files, only copy. I've tried dragging and dropping, but that won't work either. I know this hard drive works because I've tried copying things onto it from my PC and it works just fine, so it's the Mac that's having the issue. Is there any way I can force it to paste files?

The drive is formatted as NTFS, which Macs can only read, not write. Download and install NTFS-3G. It's a free NTFS driver that will allow you to write to that drive. Then you can drag and drop whatever you want.

The drive is formatted as NTFS, which Macs can only read, not write. Download and install NTFS-3G. It's a free NTFS driver that will allow you to write to that drive. Then you can drag and drop whatever you want.

What is the file system on the external drive?
Macs can't write to NTFS.
There's a hack here, but it would be far easier to just network these machines and transfer the files directly.
http://www.lifehack.org/articles/lifehack/how-to-read-and-write-ntfs-windows-partition-on-mac-os-x.html
http://www.mac-connect.com/