How to lock any folder in windows xp without any software?
Steps to follow:

1. Create a Folder in C drive rename it as “abc” without quotes.
2. Open Command Prompt from Start Menu.
3. Type “attrib +s +h C:\abc” without quotes and press enter.
4. This command will Make your folder invisble and it can not be seen even in hidden files and folders
5. To make it visible again type “attrib -s -h C:\abc”
6. You can lock any other folder also by changing the location C:\abc to address of your folder.