dude i have had the same problem since I got my laptop. very frustrating...
the @ symbol and the quote symbol were swapped...
to make matters worse I was getting european characters with key combos.
after months of ignoring it I finally tracked it down.
try this.. control panel -> regional and language options -> languages -> details
first try 'key settings' and untick the boxes to swap between keyboards.
but that wasn't enough for me it still kept changing keyboard layouts!
(what the hell, what stupid shortcuts microsoft, don't you know Ctrl-shift is
often used to select text, and at least it would be nice to turn it off.)
so I simply removed US-International and UK keyboards leaving just "US"...
and hey presto I have a normal keyboard layout FINALLY. jeez. crazy.
hope that works for ya. if not check out sticky keys, or i read somewhere else
to try pressing left and right shift with Alt...? didn't do anything for me but.