Shall I upgrade to windows 8 or keep my windows 7?

[Blas]

As Edward H says - Just slap Start8 onto it and you'll be right back into a User Interface just like Windows7 - only more secure and faster.

And it (Start8) costs less than five quid!

http://www.stardock.com/products/start8/features.asp

And it gives you the Start button (or a flag) back in the bottom left corner again!

Just read today though that Office 2003 and older doesn't work in Win8, though later versions of Office are ok. Mind you, there's always the free Libre Office if necessary.
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I upgraded to Win8 Pro from Vista because it was cheaper than Win7, but since you've already got a perfectly good Win7 I reckon you'd just be spending money for the sake of it really - unless you LIKE spending money and want the latest thing regardless,