The most common reason I've seen for this is hardware related. More precisely, hardware drivers.
Start by unplugging any USB gadgets you might have plugged in except for the keyboard and mouse. If you have multiple monitors, leave just one attached. Another thing worth checking out is your video card. Do you have a PCI or AGP card as well as an onboard card? If so, try removing the video card and use just the onboard card. If there are any other cards (Ethernet, Wireless, etc.), you might try removing those also.
Please take a look at the following article:
Upgrade stops responding (hangs) at 62% when you upgrade to Windows 7
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- Marked as answer by Cloud_TSModerator Wednesday, February 06, 2013 7:09 AM