Change extension of all files in a directory in windows

change extn of all files in current dir to pdf using comamnd:
ren  *  *.pdf

change extn of all files in current dir to xml using command:
ren  *  *.xml

change extn of all files in current directory having extn txt to extn xml using command:
ren  *.txt  *.xml

Lock a folder in Windows without using any software

 lock any folder in XP

Lock any folder without using any software. Just Follow these steps:

1. Suppose you have a folder named abcd in D:\abcd.
2. In the same drive next to the folder create a new notepad file with the exact statement
ren abcd abcd.{21EC2020-3AEA-1069-A2DD-08002B30309D}
3. Now save this text file as loc.bat
4. Create another notepad file and type
ren abcd.{21EC2020-3AEA-1069-A2DD-08002B30309D} abcd
5. Save this as key.bat
6. Now there are two batch files. Double click loc.bat and your folder will change into Control Panel and its contents cannot be viewed .
7. To open the folder double click key.bat and you get back your original folder.
8. For more safety keep the key.bat in another location . Only for unlocking copy paste to the original location and double click..

(don't forget to replace abcd with the folder name)

Ref:- http://sites.google.com/site/mukeshkmrgarg/lock-folder