No browser is safe, it's like saying Macs don't get viruses.
What's true is that the browsers and OS's that are not widely adopted are not as targeted by virus makers.
Because when someone wants to make and distribute the virus, they want it to spread as widely as possible, thus they tend to write it to explicitly infect the widest audience possible.
There's all sorts of malware scanners. Also know where you are clicking.
Some of the most infected sites have to do with hollywood gossip. So the next time you click on that link showcasing Lindsay Lohan's troubles....
Also what works if you can't fix it is to reinstall windows. You can do a repair install, or reinstall it on the same drive over the old one. Or you can do a fresh install.
Fresh install does wonders but the drawback is that you lose your programs and have to reinstall them. You can export your passwords and login in info before you do any of this. You can also, at least with firefox, do it afterwards if you google how to do it.
I also highly recommend having multiple hard drives, and putting your data on a separate drive. Thus say c:/ is your boot drive. But d:/ or whatever is where you put your data.
That way when you reinstall windows and clear the hard drive you don't lose your important data, just the hassle of reinstalling core programs. Oh and make sure if you have steam it isn't on your boot drive either as you don't want to have to re-download a few terabytes.
Another way is to partition your drive, so you can make one hard drive appear like 2. Or more even. But this is best done when the drive is empty. I still recommend 2 hd's (at least).
If you buy another hd, buy a solid state hd. Make it your boot drive. It's much faster and will drastically speed up the various malware and antivirus scans.
Most viruses come from websites. It can come from more nefarious places such as peer to peer sharing networks.
Some viruses are pretty much impossible to get rid of without a new windows install. Some you need to spend many hours doing all sorts of stuff manually deleting files in safe modes and stuff. Some can break aspects of windows itself. Some steal your data. Some turn your computer into a zombie which can be used in conjunction for mass hack attacks.
So be careful and just remember a boot drive is a great way to quickly reinstall windows and get back up and running. Just make sure you keep the data on another drive, and copy and paste your my documents, pictures, saves, etc. I suggest copy and paste because then you can remember exactly where to put it, the directory structure, if it's say game saves.
I too use adblock.