There are a lot of fine software installed on your computer, you know them well: MS-Office, WinZip, Windows Media Player, Real Player, AcdSee. Most of them have no password protection, so anyone who shares your workstation can launch one of these applications and use it to browse or modify your data that was created by it. You don't want to have to learn to use new software that have the password protection feature, but you do want the password protection feature for your existing software.
Password Door can add password protection to any program on your computer. It will not modify the original programs, so it will never destroy the programs and you will never lose data.