Its usually a fake screen to trick you to call a number and pay money
Please do the following in Internet Explorer
Click Tools (the gear wheel top right) than Internet Options
Click on the General Tab and Delete all Temporary Internet Files.
Than click the Advance Tab and click Reset
Then restart the computer and it should then be gone.
I can also do these steps for you, and have made a request via Additional Services. This is optional, and if you choose to do this, I can, with your permission, remote into your computer while you watch and do all these steps (and deal with any problems that arise during them) for you. Or if you do not choose to take this service, we can continue here. This is no problem at all. Just let me know please.
Else let me know the results please.