Want to buy anti-virus

Recently I was looking to buy anti-virus software to my computer. Most sites recommend a bitdefender company.
This is good software? And if I buy the software from a third party. Or an authorized seller. It's the same as the company's official site? Official site very expensive prices ...

Depends on the Authorized reseller and third party site. There are tons of scams around, so be careful when looking around. I would try reputable sites for these types of things.. For example, I use Amazon.com quite a bit for software... You can also check out newegg.com.

More than two weeks I've been doing search...I searched on Google this week the best antivirus 2010. I found a company called anti-virus4u.com. I bought out a really good price, software that many say is good. bitdefender antivirus. I got more than half price discount...I am really looking for a lot ...

Can I install on my computer two antivirus programs together?
Or Anti-virus software and Internet security software. Together?

you should know, that very often you can find a discount(coupon) for you antivirus software. Usually it's about 10% off, but sometimes up to 50% , but it is time limited offers.