Computer infected

I went on the internet and al of a sudden it kinda shut down and this thing cam eup saying that all my files had been infected with tonns of worms, trojons (?) and stuff like that and saying that my documents and my c: drive was too. It was strange because I know I am already protected by my norton 360 which I payed like £60 for and I always scan my computer. When I clicked on the thing to install this new protection thing it came up with all the pay form thing for lisencing with them. I then came to the conclusion that it was all just a big scam thing to get me to sign up with them so they got my money. My problem is this: I cannot seem to remove the downloaded software. I have tried right click deleate and gone to add or remove programs but its like it has hidden itself somewhere, it is not on the list to remove, and also when I go on to my programs and go on the icon and click uninstall it just doesnt even cum up with owt!!! the antivirus that is trying to get me to pay is calling itself ‘’’personnel anti virus’’’ do any of yhu know about this?? how can I get rid of it!!! pop ups keep cummin everywhere and saying I got a critical system warning when I actually don’t !!

Please help me I wud be sooo greatful!!! Thankyhu xxx