The pop ups are pointing me towards a variety of websites, some of which the Norton flags as a threat, some of which are naughty, some of which are dating and some of which are even legitimate sites!

I don't know if I got rid of them properly, but none of the detection tools I've downloaded can find them now.

I have since used Spy-bot, which found a virtumonde trojan, but I've tried to remove it three times and it keeps returning to the registry after I've allegedly removed it!