Sorry, didn't explain too well.
Firstly I had only been 'gone' about a week.
It's not just the mountains, (I was using those as an example), but most straight lines have a jagged appearance to them now.
It wasn't the F1 button, I made sure I was on the right view setting. I seem to remember ages ago someone saying something about 'Anti Aliasing' making jagged lines disappear, but I believe that was a setting on the video card, not in the game.
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