I like to keep some pretty large archive folders on my computer. Is there any Security Properties in Windows XP that I could put on the folder to ensure no virusses or other garbage get into the folders? What if I set the read only setting to the top folder in the archive tree? Would that ensure 100% that a virus couldn't enter it?
There is no security setting that will provide 100% protection. Any virus or malware that manages to run with administrator privilidge can do what it likes. This is pretty much true of any OS, not just Windows. If the stuff is valuable get a Linux box (eg Ubuntu), keep it on that and make all the files read only.
Hopefully you keep your computer patched, have Anti-Virus software installed and running and updated, and your computer sits behind a firewall router device and/or you have a software firewall running. Also, to be safer you should avoid reading email or surfing the web on that computer, use another computer for those activities. All this limits your exposure but there is no guarantee so keep a backup too. Al that said, if you must, access the web or read email from that computer do so logged in as a standard user account that doesn't have admin rights and doesn't have access to those folders. Setup another account that does have permissions to them and do a "run as" that other account to access them. Still, no guarantees really. All you can do is take precautions to reduce your exposure. If it's really important stuff store it on a computer that doesn't have access to the Internet too. That would be much less likely to be compromised. Best of luck with it.