Can't drag to external hard drive anymore

Hi, please help!

I have a Seagate external hard drive and can no longer drag or even copy and paste into it. I use this to back up files from my macbook and haven't done it in a while, so I need to figure out what's wrong. Please help!

How is it formatted?

I don't know...

Has anything changed with the drive since you last used it with your Mac (for example, using it with a Windows machine)? How long ago is "in a while?"

You can find out how the disk is formatted using Disk Utility, which is in your Applications folder under Utilities.

You can find out how the disk is formatted using Disk Utility, which is in your Applications folder under Utilities.

Click to expand...

Or by Right/Ctrl clicking on it's icon, and then on Get Info.

When clicking on the "Seagate Desktop Media" tab, there is no format listed. Underneath that option there is "Expansion Drive" and the format of that is Windows NT File System (NTFS). I believe the last time I used the external hard drive was on a Windows, and I guess thats where my problem is. How do I format it so that I can use it on my Mac, and will I lose any files? Thanks so much!