is this a legitimate microsoft number 1-877-342-2334?

Microsoft will never call you. Any call that says they are from Microsoft should be immediately considered a scam. Same with Internet interference like this.

This happens to me and many of my clients a lot. The solution is simple:

1. Do NOT respond to anything you see on the screen
2. Right-click on the task bar and choose Start Task Manager
3. Make sure you are on the Applications tab
4. Select the item in the list that is your browser instance
5. Click End Task
6. Confirm if asked

Do NOT shut down your computer using the ON button or power plug, unless there is no other way to stop this. Every time you abruptly and improperly shut down Windows, you risk corrupting the system. Does not happen every time, but is definitely a risk.

As long as you follow this procedure properly, nothing bad will happen in spite of all the threats you see.

a popup screen said my computer was locked and to call this number (1-877-342-2334). I did. The man said he was with Microsoft support. Was he really?

https://www.google.com/search?q=877-342-2334 

No. That's a common scam called the tech support scam. You don't say that you gave them access to the computer or agreed to pay them anything. If you did not... good decision.

That was a JavaScript generated message you saw simply because you landed on that webpage.

If you were not able to close that window, if the computer was actually "locked" a pull-the-plug hard reboot will let you escape this as will closing all browser processes from Task Manager [Ctrl+Shift+Esc]

If the screen reappears when you open the browser, clear the cache. There's no malware installed... nothing else you need to do.

https://www.refreshyourcache.com/en/home/ 

Don

If you have given access to them, consider yourself to be in threat and the machine a disaster.

Do not allow that machine to be online again until it is completely re-installed.

Contact your credit agencies and notify them

Contact banks and credit card companies and have them cancel cards

Contact the post office and let them know

Thank you Don. Unfortunately, I did give them remote access but got suspicious when they asked me to check all bank accounts. I hung up then but am worried it's too late. what do you advise?

It's possible that software other than the Remote Connection app was installed Not highly likely perhaps, but possible. Someone else will advise you to do a clean reinstall of Windows. I think that's overkill, but it's your choice.

Let's at least find and remove the Remote Connection app.

From Control Panel > Programs and features select the "Installed on" column so that most recently installed programs are at the top.

Look for a program installed on that day that you didn't voluntarily install.

Perhaps ;

LogMeIn

MS Remote Desktop

Team Viewer

Zoho Assist

GoToMyPC

Or another...

Uninstall any of those that you find. if you find another suspicious program/app, research it and remove it if you think it's malicious.

Run your antivirus/security program. Research anything found, to insure that's not a legitimate file, and remove anything that appears to be malware.

Don