Dell Inspiron 1720 Faulty Keyboard??

My lovely Dell Inspiron 1720 notebook was working quite happily but then the next time I switched it on and used a browser it started filling the URL box with letter 'd' by itself. It then returned to work normally for a minute or so but then started filling a page with the letter 's' then 'a'. Sometimes I can get it to stop doing this by pressing another key but 'a','s' and 'd' have stopped working altogether except when they spring into life by themselves.

Virus checker says it's clean. What checks can I run to determine if it is a driver fault or keyboard hardware fault?

BTW only using built in keyboard and all the keys seem fine... nothing lurking underneath... and not had any problems with sticking keys to date. 1720 is twenty months old. Also if the keyboard needs changing it looks straight forward but not sure how to get hold of one.

Thanks for any advice!

 

I don't understand... if the "built in" keyboard works fine... what's broken? Are you having a problem with an external keyboard?

 

Sorry what I meant was that from a visual check the built in keyboard does not appear to be physically damaged, also I've not spilt anything on the keyboard that might make the keys sticky.