You use any other Anti Virus of your choice.
I would recommend MSSE. It is best for all XP, 7, 8, Vista..
You can not actually uninstall defender, however can disable it.
In Windows XP you could uninstall Windows Defender because it considers it as application that you could install but in Windows Vista and Windows 7 it is part of Windows and you could NOT unistall it. However, you could disable it.
If you are using XP, just uninstall from Add Remove program, or else use Windows® Defender Uninstaller Tool 1.0.
Although you can't uninstall Windows Defender from Vista or Windows 7, you can turn it off. To do so, click Start, type defender, and click Windows Defender. Click the Tools icon at the top of the window, then the Options link.
The rest of the instructions vary with your version of Windows:
Vista: Uncheck Automatically scan my computer (recommended), then scroll down and uncheck Use real-time protection. Click the Save button.
Windows 7: Click Automatic scanning in left pane. Uncheck Automatically scan my computer (recommended). Click Real-time protection in the left pane. Uncheck Use real-time protection (recommended). Click the Save button.
- Click Windows Start button, Type MSCONFIG in the Start Search box and Press the Enter key
- Click Startup tab, Scroll down and UnCheck Windows Defender Startup Item. Click OK to Save config change
- No need to reboot, Click Exist without restart
Additional Information (on next boot):
Windows Vista monitors the use of MSCONFIG. After you reboot and login, Vista will prompt you with a box explaining that you recently made a change and explaining how to back-out the changes if desired. Below is my recommended response to this Vista System Configuration Prompt.
- Check box Don’t show this message or start System Configuration when Windows starts and Click OK.