I'd recommend Avast as well. AntiVir is also good. It used to popup nag screens for the pay version, but they stopped doing that last year. It usually scores near the top, and was easy to use. AVG is the other popular free one, but it used to make for a heavier load on the system. You can check one of the independent testing labs like av-test.org - where Avast does well - but the first place spot seems to be tough to keep one year to the next. (See link at bottom) I also don't think it's necessary to pay for an antivirus program. If you know what you're doing and are careful, you don't really need one actually, but for the avg user it's probably a good idea. The problem is, the nastiest stuff out there is ahead of antivirus detection, so you need to stay ever vigilant with your clicks. Here is a link that might be useful: http://www.av-test.org/en/antivirus/

Here's an example of the sort of thing that can be done with it. In the first picture, choosing to give the sky reasonable lighting ended up darkening the barn to the point where the image was delete-worthy. But Silver Efex Pro not only salvaged it, but created a dramatic image that I like a lot. Other than color removal, the only change was to the lighting.

There are a number of free antivirus programs that perform just as well as ones you pay for. I paid for antivirus for many years and switched around between Norton/Symantec, McAfee, etc. But I got tired of all the changes from year to year with new interfaces, the way some versions would slow down my computer, and having to hunt for the best price annually. I finally decided to take the leap about 5 years ago with the free version of Avast. I have it on three different computers and have yet to have one virus make it past even though I am all over the Internet every day for more hours than I want to admit. It has a very clean interface, is simple to configure, and even has a password manager built in if you want to use it. If you really have your heart set on paying for software, Avast also has a paid version with a few more bells and whistles, but for me it is unnecessary. Here is a link to the free download: Avast - free download

All major paint manufacturers offer that on their sites. Go to SW for instance. Free is only so good at distinguishing the boundaries though.