Keyboard stopped working help

Hello, my laptop is a Compaq presario C700 With Windows Vista.
The keyboard has stopped typing some letters, it also types numbers where the letters are.
For example: the U key types 4.
The I key types 5.
And like that.
I tried opening it up and cleaning it. (didn't pour any liquid on it)
Just some compressed air, i reconnected everything and 2 or 3 of the keys that weren't typed are functional. I would LOVE an answer as fast as possible i use that laptop for my homeworks and it's REALLY annoying to go to internets that fills my USB drives with viruses.
I thank all of you for helping.
P.S.: Sorry for my bad spelling.
Again, Thanks