Trouble with External Hard-drive

I'm pretty new to my macbook and I have an external hard drive that I used with my old PC. The hard drive will show up in my finder and on my desktop but when I try to drag stuff into the hard drive the finder icon jumps and tells me that the device cannot be modified.... PLEASE HELP!!

Did you format the hard drive? If its still formatted as NTFS then Mac OS X can only read it, but not modify or write to it. Use the Disk Utility to format it. Good luck <><

I suggest moving the data, temporarily, to a back-up device or your old PC, and reformatting your external HD to Mac OSX Extended (Journaled) format, especially if you replaced your PC with your new Mac.

You could always format into FAT32, but I think you can only move 4 gigs at a time, maybe I'm wrong?

Once it's formatted, add all your data back to the newly reformatted HD, and now you have read/write permission on your MB.

Good luck dude!