When i first looked at your problem ... it seemed like a obvious problem, witch I won't mention.
Anyway since your problem is not so obvious... and it might still be an simple fix:
One thing comes to mind that could only interfere or coz such a problem .... *Have u checked out the power settings for your laptop in control panel...?*
But it is probably not that simple... can't be a wrong~fully installed drive either since u mentioned that on the same drive onther OS does run well ....*
drivers?*
U still have this problem after formating and it still only happens in windows 7 and not in other OS on the same drive...*{is the drive partisioned?} could be a software invection?*
well I hope this helps a bit...