Mary, keyboard problems are not invariably software or malware-related. First things first - what OS are you talking about ? XP, Win 7, Win 8 or what? What type of keyboard is it? PS2, USB or wireless?
Disconnect it and reconnect it a few times, reboot and try again. Turn the keyboard upside down, placing one end on the edge of a thick book, and thump a few times on the back with your hand. Sweep the crud onto the carpet.....
Is it just a keyboard hardware problem, and if so which keys?
http://windows.microsoft.com/en-gb/windows/keyboard-shortcuts#keyboard-shortcuts=windows-7 tells you a lot of key combinations with ctrl and shift and alt. Tell us if any or none work?
Open a document and try typing a bit of text. Do all the characters work?
If it appears the keyboard is faulty, can you borrow another to test?
Quite often, keyboard problems are down to wireless problems: and can often be solved by re-installing the keyboard driver.