SH 3

Hi guys i have decided to venture into the cool world of SH3 an am i in trouble.
Lets start from beginning i am 63 yrs,i bought this PC in oct 2009 which runs windows 7 64bit. Very rarely use games but decided its time to chill out with retirement round corner (plus wifes permission ) Anyways got SH3 cos i thought with my pc old SH5 too powerful.I have an STEAM account seen sh3 on there bought an downloaded it the game starts ok with opening film sequence,then i get a menu screen after that am in control room of sub when i leave control room the picture go,s crazy i get like treble/quadruble blocky vision an once i manage to come off the game my main pic/screen is still same i end up having to reboot pc to get back to normal, Have emailed Steam no-reply so not happy.So can any one help Please