I've been fortunate enough to own and be the sole user of the computer that I look up ASFR stuff on. For windows users on shared machines though, there are a couple of programs that might help. First...
Truecrypt is a good utility for hiding the evidence of what you're doing (not being seen is another matter, sorry)

Once you install it, you can use it to set up a file on your hard disk, USB drive, etc. Truecrypt lets Windows see the encrypted file like another removable disk and anything written to it is automatically encrypted so even if your roomie finds the file/drive, it's all scrambled. The only down-side so far is that you can't use this if you're logged in as a "guest" account, but most people using Windows have admin rights by default anyway.
Once you've got that set up, use
Portable Firefox to keep everything together. Firefox is an excellent browser and having the portable version installed onto a Truecrypt drive makes sure that all of your logs, cookies, history, etc, are kept there where they're safe and encrypted.
Since no evidence exists outside of the Truecrypt volume, all you have to do is unmount it and remove it. Even if you forget to do that, whoever finds it will need your password to get into the drive so your ASFR stuff remains hidden.
Of course, this doesn't stop people from sniffing the line between your computer and FC, or recording stuff in memory while you're reading it but we don't wanna get TOO paranoid, do we?

Here are those links again:
http://truecrypt.org/
http://portableapps.com/apps/internet/firefox_portable
"Don't sweat the petty things... don't pet the sweaty things..."