888-845-1636

Message popped up on my computer; Threatens my computer has been locked and I have to call them at 1-888-845-1636.  Threatening call; I pretty sure it is spam.  The English is poor.

Tech Support Pop Up scam:

Microsoft error and warning messages never include phone numbers.

Web Browsers DO NOT have the ability to determine and warn you your computer has an error. They can only warn you about a potential malicious website you are about to visit. A Browser is software that allows you to surf the Internet, not diagnose a computer or phone.

How would the pop up message know who to call unless the number was put there by the scammers who created the pop up? If your computer actually generated an alert, it certainly wouldn't use a web Browser to display it.

Most popups are generated from an Ad on an unsuspecting website and you can just close the tab/window. If it will not close or opens new windows/tabs, try editing the address bar {put Google.com} and hit enter or you can End Task the Browser {Ctrl+Shift+Esc}.
They can be removed by clearing the Cache and History after restarting the Browser. You should also have an Ad Blocker turned on. If your Browser doesn't have one built-in, you might look to see if it supports a Browser Extension Ad Blocker.
If that didn't work and your still getting pop ups, you might have a PUP (Potentially Unwanted Program) that triggers a popup window.
You can goto https://www.malwarebytes.com/mwb-download/ and get the free trial to remove it or you can try this site to help remove the PUP:
https://malwaretips.com/blogs/remove-tech-support-scam-popups/

Beware of websites claiming "Remove 'this number' pop up virus", as many are downloads for adware cleaners or malware containing scareware. Only trust reputable Malware/Anti-Virus sites that use Official products from the Official website.