Blanking out the hard disk would be a probable senario a few years back but I think most manufacturers [probably not Acer] have learned not to put the rubbish in the new computers. If anything, prior to blanking would be to create a copy of the recovery DVDS just in case wiping the driver doesn't work perfectly.
Of course you also need to have the media that corresponds to the version of Windows 7 installed.
Finally by wiping the recovery partition, if something happens to your copy of Windows ....
After installing Windows 7 and before you put anything on it, image it.
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