If you get pop ups on your computer is it dangerous to do online transactions?

i have got this virus thing called 'My Security Engine' that always pops up it has 3 different ways of popping up... one where it makes a screaming noise and makes me have do close it (i cant just carry on with what im doing i have to click X then it says are you sure you want to continue unprotected?) as if to make out its a virus protection download (when ironically its a virus itself) also im starting to get other pop up when i go on websites, no matter what the website is it pops up and a womans voice comes on saying 'congratulations you've been selected for the questionnaire' blah blah and it has the name of the website im on (eg if im on ebay it says in big writing at the top of the pop up 'EBAY') to make it look as though its official... they're really annoying me now and im just wondering if i was to make a transaction over the internet for example buying something off Amazon or eBay, will it be dangerous? Will the pop ups be the kind where they can find my card details etc? i bought something off eBay earlier and im just worried. Id also like to say, the sad s who make viruses are the most pointless people this world has produced :S they're just weird!