For a technician with a properly outfitted repair shop, that's a piece of cake, but, for a computer user, sitting at home it's a bit more complicated.
First off you need a good cloning program like Norton's Ghost, or the cloning software from Maxtor or Seagate on a bootable CD.
Then you could do a "Disk to Image" of your old drive, storing the image file on an external USB drive.
Then remove the old drive and replace it with a new one.
Reboot the system with the Bootable CD, mentioned above, and do a restore of the backup "Disk Image" to the new drive. Job done.
As a working PC-tech, I do this stuff quite often. But I also have Ghost on a boot disk and an External USB hard drive that I can use in the process.
There are several other options available to me, but what I've outlined here is probably the simplest.
Good Luck,
The Shadow
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A person with experience is never at the mercy of a person with an argument.