Acer Aspire?

Michael you must have influence on my computer as all faulty letters now type. You were porbably right its a bad habit of eating when typing.
Gave the key board a very good brushing with a small bristle art brush turned it over so all muck dropped out and spent 1/2 hr cleaning and it worked. So would say correct it was muck stopping full depresions of the keys.
Thank you.

Bob UK
August 2015

You have been eating cheese rolls at the computer - (probably held in your left hand) - crumbs have fallen onto the keyboard and have become wedged under the key caps.

It is often possible to remove the key caps to allow cleaning - but it's a fiddly job - look on youTube for instructions. Or take to a repair shop.

Michael Dell
August 2015