Before I give you any help, I'm going to go ahead and insist that you change the title of your post from your email address. Seriously, if you want to get a huge quantity of spam, this is the way to do it.
Now, when you say you replaced your old external hard drive, do you mean you just bought a new one?
I think the easiest way for you to recover your files from this drive if Windows is not recognizing it would be to download and burn a Linux live CD, like Ubuntu (
link). The Ubuntu website has a very easy to follow guide of burning the CD, so I won't walk you through that.
Once you've burned the CD, put it in your CD drive and reboot your computer. You should boot to the freshly burned Ubuntu live CD. When you get to the menu, select "try ubuntu without installing." It'll take a little while to load up, but when it gets to the desktop, you need to go to Places (top bar)-> Computer. This will open up a window where you'll be able to see your old drive and your new drive and your HDD. Copy all the files you need.
Hope this works!