Make a image of your disk!!
You can use seagate or WD free versions of Acronis.
Back up your C: drive and the system partition if you have one.
http://support.wdc.com/product/downloaddetail.asp?swid=119
http://www.seagate.com/ca/en/support/downloads/discwizard/
Even though the upgrade/rollback may work, guaranteed its gonna leave some trash behind, and if it doesn't work, you have your saved image to use to restore your computer.
I will attach a copy of Seagate bootable media that you can burn, even if you don't have a seagate drive, this version will let you use it if you hold ctrl and type t then o when the box comes up saying it cant find a seagate.
This will save you much frustration and possibly all of your life's work.
I'm including this bootable version because it lets you use the program without the hassle of installing the main program.
http://www39.zippyshare.com/v/CuItqU3H/file.html
MD5
566f877338eafbeb1beb16d549955b1b
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