Need you to check the event viewer logs for both operating systems for any error reports that might show up.

control panel > adminastration tools > event viewer....when the window opens there will be 3 logs in the left pane. Click on them one at a time and see if there are any errors reported from the logs. Scroll down the page...

if an error is seen then highlight the error and dbl clk to bring up a more detailed explanation.

I am thinking that you might also have a harddrive problem as squirelandmoose suggested.

Also, did you happen to download any updates or fixes right before this happened.
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