At a guess, some rogue process is running in the background and is occupying a huge number of your CPU's cycles. Have you done ctrl/alt/delete and run 'Task Manager'? Click on the 'Processes' tab and see if you can identify something that's occupying a large amount of your CPU resource. (If you click on 'CPU' in the heading, it will arrange the results in ascending (or descending) order. Let us know what you find out.
Oh and, re the keyboard - you have forgotten to select UK keyboard when you reinstalled Windows, so you now have an American keyboard where the @ and the " are transposed. It's easy enough to change it back.