Combination of Problems-Computer Is Locked-Wrong...

Question

When beginning --under my name it states to type my password--there is one that has been already put in --it is not mine--don't know what it is since there are dots that appear--when I try to delete it-the little hand keeps blinking and I have to try about five times until I can delete it and put mine in.

After computer is on for a few minutes (I cannot get online) a notice comes on and states "The computer is in use and has been locked." Only Toshiba user Catherine Krupsaw or an administrator can unlock the computer. Has my user name and space for Password--I do not know
my password--my son thinks it is my name--however I cannot put a "k" in anything since it is not working on my keyboard.

Can one letter be replaced or do I have to buy new keyboard?