This sounds like a driver problem and a quick fix is to trick Windows 8 into thinking your resolution is higher. There is a complete guide here.
- Open the registry editor Win+R and type in regedit
- Find the following key
Display1_DownScalingSupported. The location is different for every driver
- Set the value to 1 for every time the key was found
- Now you can change the resolution to higher values
In your case it is not really clear what happened. You installed Windows 8 and then Windows 8 told you that your resolution was incompatible?
These sound like the differences between regional keyboard layouts. You should verify what your keyboard layout is set to. Detailed instructions can be found here. The cause of the problem maybe that the method says 'UK' when it should say 'US'.