PartLocker

PartLocker is a small-sized and portable Windows utility whose purpose is to instantly lock drives on your hard disk. It comes in handy whenever you share your computer with other users (willingly or not), since it helps you restrict access to private information as well as sensitive Windows files.
As there is no setup pack included, you can put the executable file anywhere on the disk and just click it to run.
There is also the alternative of saving PartLocker to a USB flash drive or similar device, to be able to run it on any workstation seamlessly, without installing anything beforehand.
In addition, the tool does not create new entries in the Registry or Start menu, leaving the disk clean after removal.
The user-friendly UI consists of a single, small window with a clear-cut structure, where all you have to do is select a drive's letter from the drop-down list to lock it with the click a button. A secondary button is responsible for reversing the process.
The new changes are immediately applied to the disk, once PartLocker restarts the Windows Explorer process. The drive in question is not hidden from the list. However, it will pop up an error message whenever any access attempts are made. The only way to unlock it is by using PartLocker.
The tool is not foolproof, unfortunately. Since there is no option to protect it with a password, basically anyone can use PartLocker to lock drives at will. So the best option here is to keep the app somewhere safe, where other people do not have access.
The program has a great response time and uses low CPU and RAM. It did not cause Windows to hang, crash or pop up error messages in our tests. In conclusion, PartLocker offers a simple and secure solution to restricting user access to selected drives.