Copying files to an external Hard Drive

Hi guys. I'm new on mac...
I'm trying to copy files from my iMac to an external Hard Drive, but I couldn't... I'm just able to read files...
How do I do?
Please Help me...
I rather get the reply today...
Thank you a lot
Best Regards

Elias Lattouf

Its probably a Windows formatted NTFS drive

Macs can read but not write to that drive format

You can either reformat the drive to Mac HFS or install MacFuse to give the Mac the ability to write to NTFS drives

Downloads - macfuse - Project Hosting on Google Code

Thank you Louishen
You're really so kind
Best regards...