1) Virus
It's more about how good you are with using your computer. I haven't used a Virus software for years. I have one installed, but it's turned off becuase I find it completely takes over my computer and slows everything down. But . . . I know enough about it to not do dumb things that would introduce a virus or trojan horse. Some dumb things include:
a) Opening emails and especially attachments from people you don't know. Just delete them. If it's important, the person will email you back.
b) Frequenting shady sites (casino sites, porn sites, etc).
c) using P2P sharing networks (LimeWire, Kazaa) for movies, music, video's, software
I usually run a virus scan once a month to make sure I don't have anything. In 6 years, I've never had a virus. I personally think the IT industry has cooked up virus fears to make people think they need all of this software protection. Don't get me wrong . .there are nasty viruses . .but if you are careful, you can get by without virus software. Oh . . .you may get a free antivirus software from your ISP, so check with them first.
2) Loading software onto other computers.
Definitely illegal . . . but . . .the likelihood you'll get caught is nill (though, more and more software providers require activation for each install). As a software developer, I frown on loading software willy nilly . . .but . . . if you want to do it, you're really not going to get into much trouble. Trust me . . . Adobe really doesn't have the resources to care that one residential consumer is loading Photoshop onto their computer illegally. They care more about corporate abuse as it's easier to identify and prosecute. There';s no way they can go after all of the individuals doing it (despite their curt terms and conditions). I personally wouldn't do it because I just don't think it's right . .. . .but there are plenty of people that do it without ever getting caught. It's extremely difficult to get "caught".
As for photo-editing, it really depends on what you want to do. I mean . . . Photoshop is pretty amazing . . but . . you likely don't need all of that power. Just go to Downloads.com and search on photo-editing. I'm sure sure you'll find a free one that does basic editing nicely. Also, when I purchased my Kodak digitcal camera, it came with a decent photo editor.
Hope that helps.