One of the after effects of a particular virus - which one I am not sure - is the inability to see hidden files and folders. I've generally seen it on the same machines where I have seen the Hacktool.Rootkit virus problem I mentioned before.

Anyway, from wherever it arises, the point is you are not able to view your hidden files and folders. Even if you reset the option in the Folder Options dialog of Explorer, the settings do not have the desired effect.

Here's how to fix the problem

Open a Notepad and copy and paste the following content in blue into it.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced]
"Hidden"=dword:00000001
"SuperHidden"=dword:00000001
"ShowSuperHidden"=dword:00000001

Then save the file as "one.reg", remembering to type in the double quotes around the file name.

In Explorer, go to the folder where this one.reg is stored and double-click on the file. You will be asked if you want to add this information to the registry. Click [Yes]. (you may now delete this file if you like, it's purpose is solved)

Log off and log back on and you will be able to see your hidden files again.

After doing this you will be able to modify the Hidden Files setting using the Folder Options dialog again.