Many Balloon errors, Malware and Trojan warnings. Windows opening on their own.

I left for the weekend and the babysitter was on my computer and now it's just plain messed up. When the computers on, it's always hooked up with highspeed internet. So now if you set and watch the screen it opens up to 50 windows in internet explorer an hour by itself. A balloon opens up at the bottom of the screen and says multiple different things like trojan virus found, malware found, and many more. And it opens up windows that says micro trend has blocked it, and it's to some site called kukkakreck. I've updated virus software, bought additional spyware and nothing fixes it. I'm not all the bright with computers and a friend referred me to this forum. Please help if you can. I'm using XP home edition. It also has put 2 icons on my desktop, one is called LIVE SAFETY CENTER and the other is called ONLINE SECURITY GUIDE. I ran Hijackthis but it won't let me post it, It says it contains the word "a s s" but I read it 4 times and cannot find it.