How Do I Transfer A Project File Created Using iMovie 7 To A Hard Drive?
I’m not sure I understand you… you created a Movie Project in iMovie 7 (which if I’m not mistaken is the iLife ’08 version) and now you want to move it to an external drive?

You don’t mention your Mac OS X’s version but that shouldn’t really make much of a difference.

Ok should the above be correct, you have to locate your project in your hard drive. It will be probably located in your Movies folder. Assuming you have connected your external drive and the drive is ready to use (i.e. Partitioned and Formatted) for OS X, you simply have to open two Finder Windows (use CMD + N to open a new finder window).

After you have the two Finder windows, navigate one to where you see the project in your /Movies folder. and in the other Finder, go to your external drive. 

Click in the iMovie project and Drag it to the other finder window (don’t release the mouse/trackpad button). When you reach your external drive, release it. 

It will be copied, not moved. When the copy is over, simply drag the old one to the Trash. :)

I’m sorry if this sounds too simple (or too complicated), the thing is that the nature of your question could be as simple as “how do I copy a file in OS X” or as complicated as “I got a new hard drive and I want to use it”. Both things are not complex, but the instructions for each are completely different. :)