Joe_ Bellini :
The pc is mine (beware not to suggest laptops, I cannot stand them) and I put it in the cafe-room. It's impolite to prevent my mates to use it. I just need to make sure no one gets into my working/personal files.
Then why are you putting personal files on it?
Stuff you don't want others to see.
If you must...your "D" drive should just be a USB stick you take with you.
Given physical access...any drive in that system is accessible, no matter what you do.
"Oh...I know Joe has a hidden drive in this. Let me boot up from a Linux CD and see what is on there."