Assuming you have a firewall and have got Automatic Updaes turned on:
1. Click Start and then click Control Panel.
2. Double-click Security Center.
3. In the Security Center, under Virus Protection, click Recommendations. (The Recommendations button is not available when your Virus Protection setting is marked ON.)
4. In the Recommendations dialog box, select the I have antivirus software that I'll monitor myself check box, and then click OK.
EDIT: Or
Press the Windows and R keys > in the resulting window type services.msc > in the resulting window scroll down to Security Center and double-click on it > In the "Startup type:" box use the arrow to scroll down to choose "Disabled" click Apply and reboot, or, click Apply and click the button that says Stop.