Personal Antivirus-- How do I know it's off my computer for sure?

So, a couple months ago, I got an ad pop up saying that I had a ton of viruses on my computer. In a hurry, I quickly clicked on an installment button. I know what you guys are all thinking “How could you fall for that?!?!” well… too late, and I did! =(, I’m such an idiot sometimes.

Anyways.. so I spent the whole day trying to get rid of it, it got harder and harder as time continued on; the longer I had it, the worse it was getting for my computer. More pop ups would come onto my screen, more false pop ups saying that my computer was infected with viruses and also internet access was extremely difficult.

How I had gotten rid of it, was from youtube, it took me a while to get onto there because Personal Antivirus would keep closing it on me, and it also denies access to a lot of things on my computer. I was so frustrated yet I had to keep it to myself. (I frantically messaged people to ask for their suggestions, and trying not to seem panicky to my siblings who were around me or else I’d have been in big trouble).

After hours of following a guide for “Manual Removal for Personal Antivirus” from youtube, it seemed as if i was successful in removing Personal Antivirus once and for all. I was so relieved.

So it’s been months since I got rid of Personal Antivirus, and today, as I was just on various websites, one of Personal Antiviruse’s familiar ads popped out onto my screen! I thought it had disappeared?, Is it still in my computer somehow?

I went to start—> all programs—> accessories—> system tools—> system restore, but Personal Antivirus prevented me from using it. So, I went to youtube again, I restarted my computer and tapped f8 continuously to boot in safe mode…. forgot what else I did next, but then there was the option of ‘system restore’. I clicked on it, and set the time to yesterday and then my computer was fine again.

What should I do next? I want to prevent my computer from Personal Antivirus, but I also want to keep it a secret from my siblings…. is there anything I can do to prevent future problems with Personal Antivirus? Does this also mean that Personal Antivirus is still in my computer somehow? (I had installed AVG’s free edition scanning after a friend had suggested that I should)

Sorry for the big blob, but if anyone has any helpful suggestions, I’d really appreciate it!