I am using an ATi Radeon graphics card and I currently downloaded the 11.4 driver update as I heard it is good for Witcher 2. How can I check to see if it installed properly and that i am using this version. I apologise if this is a stupid question or if I am missing out some key info, but i don't know much about this stuff.

What OS do you use?

It depends on your OS, but seeing as you're wanting to play The Witcher 2, I'm assuming Windows.
To check, open the Catalyst Control Center, make sure it's on advanced view, then go to Information and then Software. The driver version will be listed there (under "Catalyst Version").

Open your run box, and type in "dxdiag", and navigate to the "Display" tab. Check the date, and if it's...recent, that's the one.

Right click on the dashboard, and all the way up you will see the C-control center button. Left click on it and go all the way down to information. Then choose software information.

Wow, what a great question. I have always used the Catalyst Control Centre method, now I have other ways of finding out too, that's pretty cool.