Suddenly cannot see any folders at all, but they're there

I am suddenly having trouble seeing or finding folders and files in my hard
drive. But when I check for free space under properties, I know the files are
still there since the amount of Used Space is still the same as before. When
I open up Microsoft Word or Real Player, I can still load the files listed
under "Most Recently Viewed" section, but when I actually go into the C
drive, none of the files show up.

I suspect that this is due to a virus, and I have run a full system scan to
remove any threats. But I still cannot see any folders or files.

After detecting this problem, I tried copying some photos into a new folder
on my hard drive. After it finished copying, that folder could not be seen
anymore, although the files are definitely on the hard drive as the amount of
Used Space increased.

I have tried going to Control Panel, Folder Options, View, and then select
"show hidden files," but it still doesn't work.

Any help would be greatly appreciated. Thanks in advance.