The virus use this block as a protection to hide its files and prevents the healing process.
When you try to set the Show Hidden Files and Folders to Enabled it reverts back to Disabled after you click on OK. Sometimes you don't even have access to the Folder Options settings at all.
There are several ways to fix this problem. It depends on the complexity of the virus:
1. Use the tool DiskHeal from Computer-Realm to bypass the blocked Show Hidden Files and Folders.
install the tool and run it. on the Fix Menu click on the button "Fix Folder Options inaccessibility".
2. Using Safe-Mode and Login as a different Administrator Account
Most viruses does the blocking by using Windows own Local Group Policy. the policy is applied on the Current User Account and only on some cases on the Local Machine. Therefore by login-in as a different Administrator user you can bypass the block. Using Safe-Mode as a trouble-shooting environments is also wise because most group policy rules are not working in that mode.
3. Cleanup using an external Boot CD
You can use one of those custom Mini-XP boot CD's or Microsoft's ERD Commander to get access to the system's Registry, Autorun settings and file system. Than you could delete the problematic virus files, either manually or using an anti-virus scanner. One of my favorites boot CD's is the Hiren's BootCD. the latest 9.8 version includes a custom Mini-XP that runs from your CD and gives you a great Explorer shell to troubleshoot Windows. you can download Hiren's BootCD using this Torrent.