computor question

I am assuming I might have some virus??? (even though I have an anti virus)
Two reasons why:
One is the other day I added more time onto my cell phone via the internet which I what I have been doing the last few years. The next day I was notified by the cc company that bizarre charges were on my card...so its been closed.
Second is I keep have to reboot the computor. I can come home tonight and check online and it comes up nothing. So I reboot the computor AND have to turn off the modem for a short while. Then turn them on and all is fine till the next day.

Does it sound like a virus? Needless to say, I am not using my cc online for anything anymore. If it is, what is the best product to buy? What I also want to do is clean out this thing, a lot stuff on here I don't need which might be the reason it keeps shutting down. I have photos/video on here. So what is the best product for this?

Thanks

Based on what you said and the fact you didn't say if you're virus scanner picked anything up at all I'm going to say you may have a virus but with out more info I can say you do. Could a ton of reasons why your sys is rebooting like that. Here are just a few of them. Power supply is dieing, motherboard is dieing, the box is getting over heated, you may have a progy set to reboot once it's done doing what it does and not even know it. As for the CC thing you just might have over the years been tricked into using it some place you shouldn't have or used it on an unsecured site and someone picked it up.

If you have a virus scanner why are you asking what the best one to use it? Use yous and if it doesn't pick anything up then good. If you want a 2nd opinion use http://us.trendmicro.com/us/home/ If you are satisfied after that take to an IT dude and have him check it.