You can do this by creating a new archive without a password .
Open the WinRAR and right click on the RAR file that has the password you want to remove.
Select "Extract files" from the list of options.
Enter the RAR file's password in the window that appears and select "OK."
This will extract the archive's contents into a folder in the same directory that the RAR file is in.
Now right click on the New folder , ie the one which is newly created and select "Add to Archive."
This tells WinRAR that you want to take the files in the folder and place them in a new RAR file.
Select the "OK" option in the window that appears.
Now the files in the folder then will be added to a RAR file.
When WinRAR finishes creating the archive file, you can access it without password protection.
UPDATE:
The above post is useful only if you know the password and want to remove it , but if you dont know the password then its practically very very hard and almost next to impossible !
You'll need an archive password-cracking program and that doesnt come free
- www.brothersoft.com/.../remove-win-rar-password.html
- www.rarpasswordcracker.com
- www.sharewareconnection.com/rar-password-recovery.htm
these doesn't come free , so you need to purchase these shareware !
Go to a website where you can download a program for breaking a password on a RAR file.
Download and install your archive password cracker.
Open this software and find your file.
Choose the option you prefer in the "type of attack" box.
The software will go through letter combinations, to find your password.