Hi,my problem is windows defender security has disabled my computer,

You are dealing with a well known scam.

Scammers will use pop-ups or web pages with screenshots of fake Microsoft Defender Antivirus or other fake anti-virus software displaying bogus warnings of malware infections to scare victims into calling a toll-free support number in order to remove the malware. These criminals may even trick an unsuspecting victim into purchasing a useless and high priced support plan.

• Scam of the Month: Windows Defender Pop-ups
• Fake Windows Defender Security Scan scam
• Fake McAfee Computer Infected With Potentially Critical Viruses scam

In some cases, pop-up alerts about "Warning! Virus Detected” or similarly worded warnings may be related to spam Push Notifications that pretends to be from fake or well known antivirus companies such as McAfee, Norton, or Avira and tries to trick you into thinking that an antivirus scan has detected viruses on your device.

Microsoft does not make unsolicited phone calls, display pop-up alerts in your browser to call a support number or send unsolicited email messages to request personal or financial information or to fix your computer.
 
Microsoft: Protect yourself from tech support scams

Quote

• Microsoft does not send unsolicited email messages or make unsolicited phone calls to request personal or financial information, or to provide technical support to fix your computer
• If a pop-up or error message appears with a phone number, don’t call the number. Error and warning messages from Microsoft never include a phone number.

 Microsoft and others have been warning folks about Email Phishing Scams and Tech Support Scams for years

Closing the web browser and then relaunching it usually eliminates the bogus warning message and is the best way to deal with these scams. If the browser freezes or hangs, you may have to close it with Windows Task Manager by selecting End Task. Afterwards, you should also clear your browser cache.

For more information about how these scams work and resources to protect yourself, please read Beware of Phony Emails, Phone Calls, Tech Support Scams (Post #13)...there are more suggestions near the bottom for dealing with scams.