OK...
First of all, if sites are bullying your computer into installing Spyware or porn, get Firefox and the Adblock extension... and Lavasoft Ad-Aware to clean up MSIE's mess. For the extremist, google nLite, and configure your Windows Setup CD (2000, XP, and 2003 only) to not install MSIE to begin with.
Second of all, if you're downloading ROMs from HTTP/FTP, you're asking for trouble. Use filesharing, that's what it's for. You can find any individual ROM you like, or you can download a ROM pack. I found a ROM pack with 800 SNES games. It says it's all the US games. I'm not so sure, but it has all of my old favorites. I've downloaded N64 ROMs but my last and current computers, on which I've tried N64 emulation, don't have the specs to emulate the N64. My next system will, though. But by all accounts the ROMs were fine.
http://www.emule-project.net is the best way to go on Filesharing, by my experience. If not, well, it's a certain way to get the ROMs you want. Others recommend Ares and BitTornado, but these work completely different, use other protocols, and I'm not familiar with them.
Please help. 
