If you want to LOCK any of your private folders in your computer without any software; then below mentioned steps might help you:

Suppose you want to lock the folder PERSONAL in D drive. Thus, it's path shall be D:/PERSONAL
1. Open the notepad. Type

ren PERSONAL PERSONAL.{21EC2020-3AEA-1069-A2DD-08002B30309D}
Now save this text file as LOCK.bat in the same drive.

2. Now, again open the notepad. Type.
ren PERSONAL.{21EC2020-3AEA-1069-A2DD-08002B30309D} PERSONAL
Save this text file as OPEN.bat in the same drive.
Now, when you double click on LOCK.bat, your folder "PERSONAL" will become the control panel and nobody can view the contents of this folder.
Now, to see your folder, just double click on OPEN.bat.