No need for a new HDD and 6 years isn't old really. Don't waste money on a new drive.
Here's what to do:
Restart computer
As it is restarting keep hammering F11 and F12 (it's one of those, I can't remember so just do both)
After a while it will open into a bootup menu, here you can chose to run the CD.
Run the CD, install it over C drive
Let it do it's restarting business
Once you're back on Windows, go to my computer, right click D drive and format it.
When it restarts (after you install Windows 7 on C drive), you might find it tries to boot into D drive again. If it does that you need to go into Bios and change the boot order so C drive is first. Google "how to change boot setting in Bios", it's pretty easy to do.
Last edited by pudoc; 29th April 2013 at 02:35.