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Regarding a clean install of Win7 from WinXP, would installing another clean drive as the boot drive and keeping the original boot drive in the system help at all?
I always install my applications to another drive anyways so they are never on the boot drive. However, Windozs has a nasty habit of spreading configuration files all over the boot drive.
I already have 6 drives in my system so another is no big deal.

I have 5 drives in my main machine right now. What I do when I reinstall Windoze is simply disconnect all the other drives except the one I want to actually have the OS on, to avoid all that.
If I'm adding a new drive to be an OS drive, I'll first disconnect all but the one that has the current OS on, and boot from the Windoze disk and then completely reformat the current OS drive. Then disconnect that and hook up the new drive and install it on that.