do not reformat. it may not be necessary. do you use windows 7? it appears that the malware/virus just hid your things.
if so:
this first set of steps unhides your files.
1) Click on the Windows Start Button
2) Click on Computer
3) Click on Organize
4) Click on Folder and Search Options
5) Click on View
6) Click the option for "Show Hidden Files and Folders"
7) Click Ok
1) Click on Start, All Programs
2) Click Accessories and Find Command Prompt
3) Right click on the Command Prompt option and choose Run as Administrator
4) At the command prompt type the following and press Enter
CD \
5) Now the command prompt should show the root folder of the hard drive. Most likely C:\
6) At the command prompt type the following and press Enter
ATTRIB -H *.* /S /D
This command will unhide the files that are currently hidden. Because the important system files have a system attribute attached to them as well, the above command will not work for them and they will be skipped and kept hidden from prying eyes.
This command will take some time, so dont be afraid if it takes anywhere from a few minutes to half an hour to finish. What the command does is simple. It removes the hidden attribute from all files on the hard drive. The /S parameter tells it to search the current folder and all subfolders, while the /D parameter processes tthe folders as well.
7) Type Exit and press Enter when the procedure is complete. Then reboot your computers
try those and if they dont work just so and we will try something else.