Hi,
It might be that you have by mistake turned on the sticky keys on the system.
Sticky Keys is an accessibility feature designed for people who have difficulty holding down two or more keys at a time. When a shortcut requires a key combination such as CTRL+P, StickyKeys will enable you to press one key at a time instead of pressing them simultaneously
I would suggest you to check whether the sticky keys are turned on. Follow the steps mentioned below.
a. Click on Start and click on Control panel.
b. Click on ‘Accessibility Options’ and in keyboard tab make sure that there is no check mark near ‘Use stickykeys’.
c. If there is a check mark then remove it and then click on Apply.
Refer the article mentioned below.
StickyKeys: Press One Key at a Time for Key Combinations
http://www.microsoft.com/enable/training/windowsxp/stickykeys.aspx