It sounds like you have your keyboard and environment in windows set up for the USA not the UK (their characteras are in a different place)
In Windows XP you go into the Control Panel and find "Regional and Language options".
In XP, within Regional and Language options, there are FIVE places where you need to change US to UK.
Make sure the UK keyboard is installed under "Installed Services" and make it is the default keyboard, and not the US one.
Not sure how you do it in Vista as I dont have one to hand.