Try typing in the Command prompt window to see if the issue is replicated there as well. To open Command Prompt, click Start, click Run, type cmd, and then click OK. This is done to isolate if the issue is with hardware failure or software incompatibility. If the issue gets replicated in the Command Prompt window, it may indicate hardware failure. If not, there may be compatibility issues with the operating system.
You may find the Microsoft links below helpful in troubleshooting the issue you are facing with the keyboard.
Troubleshoot wired keyboards that don't respond or that type wrong characters: http://dell.to/14W22jO