when i push caps lock, the start winfow pops up. Am using Windows XP.

The problem can be due to driver infection or corruption, your options are to either reinstall the driver or to use KeyTweak to reasign the caps lock key to it's normal function. You may have to reasign both the Caps Lock key and the Windows key (Start Menu)... start with the Windows key and the caps lock may be automatically corrected.

Try the software first as it may be a simpler fix than installing the appropriate keyboard driver... and if it doesn't help: If you have a disk with the appropriate keyboard driver for your keyboard, reinstall that... and if not, install the Microsoft Intellitype driver.

KeyTweak
http://www.softpedia.com/get/System/OS-Enhancements/KeyTweak.shtml

Microsoft IntelliType 8.2 32-bit for Windows XP
http://www.microsoft.com/hardware/en-us/d/multimedia-keyboard