It depends on the external hard drive - is it a USB device? If so, simply boot up your machine and plug it in, and Windows should detect the fact that it is an external hard drive and install any drivers if required. It should then appear under "My Computer", and you will be able to browse through it and copy any files across as if it was an internal hard drive.

Performance may be a little slower than expected, but if you are simply recovering backed up data, then it might be worth copying and pasting everything you want and leaving it to run overnight depending on the size of the disk and the data you require.

If it isn't a USB device or want further clarification on anything I've said above, just drop another message back here and I'll try and go into a little more detail.

John