Here are four easy steps to hide your drive partitions in My Computer from your friends:-
1. Goto run type “gpedit.msc” (without quotes)
2. select user configuration —> administrative templates —> windows components —> windows explorer (click on it)
3. On right panel search for hide theses specified drives in my computer.
4. Double click it mark on enable to hide the drive and select drive the which you want to hide. If u wanted to hide all the drives which are on your system then select restrict all drives.
to make it unhidden mark on disable option.
Enjoy!!!