Specs of PC (need more info for the most part)
Try redownloading the file, something could've been corrupt
try updating drivers if that hasn't been done in a while.
Check to see if graphics settings for (Insert control panel type) have been restricted in some way, perhaps toy around with your graphics' control panel to see if you can get better responsiveness out of it, some programs don't really like certain settings or modes, so there's always a possibility