Working with a Compaq question

How would I transfer the OS, which is on the d drive, from this hdd on this compaq?
It's not mine, but a co-worker's. The hdd is going bad so I want to replace it.
Would I just use a program like Drive Image7, which I have.

That is what I would do, as long as you plan to restore the image onto a new drive on the same computer.

Ya, just replacing the hdd in the Compaq.
Seems like a good reason for him to upgrade to a real computer anyway.
Thanks for your reply.