installed windows 10 first 2 days were great then my computer had an interruption from something. A loud noise and a flash said I had virus and windows would fix it to call 1800 number. Since then it has become very slow.

Please download the free version of Malwarebytes. Update it immediately.
Do a full system scan
Let us know the results at the end.

http://www.malwarebytes.org/products

Hi cindelee55,

Obviously the machine has been injected, please perform a full scan with the antivirus software. To improve the scanning quality, please run the antivirus software in safe mode.

If you want to make a phone support, we could get the phone number here.

Contact us

https://support.microsoft.com/en-hk/contactus?wa=wsignin1.0

Best regards