Taken from the official windows forums there's a thread on the multitouch on how to get the W7 driver working.

 

Meanwhile I can't even get W8 installed, I'll try to DL and burn a new ISO.

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Its tricky, but i did it.

 

Get the driver installer started (win 7 works).

When you get to the screen right before where it says there is a fatal error, dont press finish (or start, or next, dont remember the exact wording), press Win-R, type

%TEMP%

and on that folder, locate the folder with the last modification time. Go into it, and under that folder you should find an executable file named "dpinst.exe". Run it with administrative privileges and it will properly get the drivers in place. Then everything touch related works great.

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http://social.msdn.microsoft.com/Forums/en-US/windowsdeveloperpreviewgeneral/thread/0b446695-a5ba-4135-81d9-f0d9ddeb6203