I have been phoned by techonsupport who spent an hour cleaning up my computer and feel I should take their warranty. I already have Norton anti-virus so is this necessary? I was taken by surprise by their call and am not clear how they got my number.

tech support telemarketers..........BEWARE!!!!
dont take their support.

as long as you have a good and up to date AV you should be fine
if you ever need to get rid of spyware/malware

you can download:
CCleaner
SUPERantispyware
Malwarebytes app

tech support telemarketers..........BEWARE!!!!
dont take their support.

as long as you have a good and up to date AV you should be fine
if you ever need to get rid of spyware/malware

you can download:
CCleaner
SUPERantispyware
Malwarebytes app

Thank you, they became very aggressive on the phone and I still don't know how they found me. I will avoid all such calls in the future.

No never this company is not genuine as you might think.
they will say they're windows service provider But windows is a prodduct of Microsoft INc.
So they don't provide any kind of authorization to any company to fix with the issue.
It's better don't pay single money because if you pay they yoour maney will go in vain.
So spread this words to everyone in your place and forward it to you news media too
so everybody over there get to know about this scam.

the company is in name os annex software their none of their technician is Microsoft certified because their website they didn't provided the name of the technician and their unique certification Id.