If you always want to see the newest page (it might have been changed since you looked at it), then yeah it should be set to automatic (mine is set to that aswell). In that very same screen you can set the size of the cache (settings > internetoptions > under temp internetfiles click settings)..set the size of that folder to 50 MB, it's more then enough and will prevent internet becoming slow cuz of a too big a cache
As for the windowsmessenger problem, try and install it in safemode on the account called "administrator".
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