I'd say it's premature to pay for a new HD at this point. The install issues you have could depend on something else that's not related. Please try the alternative install cd, which lacks the fancy graphics and is a little harder to get started with, but works wonders. If that fails as well then you might have a real issue.

To verify if you really have hardware issues you could use http://www.ultimatebootcd.com/ or something similar. I guess your Sony came with Windows pre-installed, and that there are a lot of tools for that as well that you could use to scan your HD for bad sectors.

If you decide to buy a new drive buy a flash disk - they're more expensive but you will gain very much in performance compared to your current disk.