External Hardrive Problems

So, when switching to my new macbook pro, got a hardrive, backed up all my files on my old pc and works fine can copy these files to my mac.

I even can copy movies from my friends macbook pro to my hardrive.

But i cant copy my files I downloaded to my macbook to my hardrive.

Why is this, how can I overcome it and why can I copy files from my friends macbook pro and not mine?

Thanks in advance.

Welcome aboard Mac-Forums

Could be a couple of reasons this is happening, firstly what format is the drive in? i.e Fat-32, HFS+ Extended?

i'm not too sure, dont know how to find out either.

click on the drive and hold the apple key and press "i", in the info pane and under the "general" drop down it will say what format the drive is in