pistitom
I can see your problem straight away,your graphics card has way too low onboard memory.8MB used is too low for a game like SHIII,you would probably need at least 128MB upwards,to render everything smoothly.
Physical memory seems adequate,but another 1GB stick would'nt hurt.
Set all your graphics options to low,then increase them one by one until you find the main bottleneck,but I can tell you now your graphics card lacks sufficient muscle mate,sorry to say that
. If you can afford it you should buy one with 256MB onboard memory,even better 512MB.
Also,get a Bios update for your motherboard,if you know the make and the site to visit.That can iron out many problems.
Keep us posted on this one,it can be cured,via hardware upgrades.