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#51
The issue with wiping the HD is that it overwrites all of the code (infected or corrupt, for example) with zeroes so that nothing is left to interfere with a new install. It is more of a precaution than anything else.
If you didn't format the partition when you installed Win7, the installer did it for you so don't worry about it.
What's important is how it is running now. I don't understand what your friend is trying to say about saving the backup having something to do with performance but it doesn't sound possible.
Have you saved a backup? Did you follow the other steps I gave you to get a perfect install, and do you have any other questions?