If you want to prevent any users to entrance your computer or network shared drives using My Computer then you can hide the all drives for example C:/, D:/ and save your data from any unknown user. But next time you can turn on the display of these drives using registry editor. Now edit the computer registry to turn off the display of drives, but be careful to work with computer registry.

Follow the given steps to hide computer drives:
• First click on Start button then type Regedit in Run option.
• Here locate the location to:
HKey_Current_User \ Software \ Microsoft \ Windows
\ Current Version \ Policies \ Explorer
• Here right click on right side of Registry editor panel and add new DWORD then put its value 3FFFFFF.
• Now close the registry editor and restart your computer after any changes to go into effect.

See Also
desktop technical support

http://computerfreetips.com/registry_tips/d_drives_reg.html