Processor and RAM are fine. I don't know anything about ATI cards to comment on that. Windows 8 is evil, and I know SOME players have been experiencing various issues with it.
You'd be better off asking for help in the Technical Support Forums, where your post is more likely to be seen by the people who can help you resolve this issue.
Other than that, all I can suggest is ensure your drivers are up to date, and try manually setting the game settings to a lower value to see if that helps.
[SIZE=3][b]Leader of [COLOR="#FFD700"]The Rangers of Eriador[/COLOR], Snowbourn[/b][/SIZE]
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