Excellent. First step is to decide which hard disk to buy. They are remarkably cheap these days. Have a look at the selection here for something that suits your pocket.
Next go to this site and either go through the route of selecting your PC or let Crucial do the scan for you.
When you've bought your goodies and installed them you need to start the Windows install. You may need to change the way in which your PC boots up but to save a bit of time, put your Windows CD in the drive then reboot the PC. If you get a message about pressing any key to boot from the CD we don't need to change anything in the BIOS.
We'll go to the next stage when you are ready.
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Do you know that we're all in line for succession to the throne? Really?
Well, if forty-eight million, two hundred thousand, seven hundred and one people died I'd be Queen.