Sites that generally contain pornographic images and that kind of stuff are very risky. Other than that you need to use your common sense. If the script doesn't sound like it could be legit. It probably isn't. Also notice the method of encryption. Rar is generally not used for holding viruses. While Zip is.
Now about protecting yourself.. I suggest trying to download a spyware firewall (e-malware, or microsoft spyware program) one of those too should be fine. I also suggest getting HiJack This and doing a search every now and than and posting on castlecops forum.. As for virus I wouldn't really worry about it most programs you DL only contain backdoor junk and trojans. Viruses are generally delivered via email.
So I wouldn't really worry about it. Most of the time PHP scripts are harmless.. If you open up a php script (zip) and something happens.. Do a scan immendently and see if anything comes up. If you get something ask a expert on castlecops about it.
Not much more I can say.. Most is just using common sense and getting a few programs to help incase of that random time.. Everyone even a security expert has at one time being infected with stuff.. Most look for stuff to infect them to help with finding ways to get reid of it.
If you need help just give me a PM and I can see what I can do.
- Steve