You might have found out that there is an anti-virus program named Windows Defender, which is a part of the operating system that mainly aims to protect your computer by detecting or Bypass BullGuard scanning spyware and malware, has been taking up the resources in your PC. In fact, most PC users prefer to install more versatile and stronger security software like Kaspersky or McAfee, so it's just a waste of system resources of using two similar programs at the same time, thus removing or disabling Windows Defender would be a wise choose to boost your PC performance.

The removal of Windows Defender is different between Windows XP and Windows Vista. Since it is not an integral component but a program under Windows XP, it could be removed easily in the control panel. To uninstall, you should run Control Panel, click Add/Remove Programs and then remove it from the program list. The whole process can be finished in a few clicks.

Under the Windows Vista however, this program is system-in-build that no clear-cut way can be used to uninstall, thus instead of remove it we recommend you to disable it.

1. Turn off real-time protection in Windows Defender interface. Then you will receive a notification saying the program is turned off.
2. Prevent it from starting up by uncheck it in "Startup" Item

However, as the disable completed, alerts would pop up regularly and constantly reminding you that your computer might be at risk. You don't have to be panic about the alerts if you have installed another anti-virus program.