Versions before 2.4.0.1 that came out in May 2005 utilized the following protection with secret keys.

You save your secret keys to a file on a floppy disk (USB flash memory drive, CD, etc) and store it anywhere but your PC hard-drive. You can put the storage medium on the shelf, but every time you start WM Keeper, you take the floppy disk (flash-drive, CD…)  from the shelf and insert it for authorization. When the Keeper is connected to WM server, you remove the storage medium.

The latest versions work differently:

You still keep your secret keys saved to a file on a floppy (flash-drive, CD, etc...) and it sits on the shelf. You don’t need to use the removable media to launch WM Keeper. All you have to do now to access your purses is to enter the WMID and the password.

So why do I still need the file with my keys protected by an access code?

The thing is that running WM Keeper will be as easy as is described above only as long as you use it on your computer under the current user account.

However, if you:

• Buy a new computer or want to access your purses from another computer
• reinstall Windows
• or change (upgrade) your PC hardware (add or remove a device),

you will need this file and the access code again.

Incidentally, the above circumstances may happen when you least expect them.

Another analogy may help: your secret keys saved to a file (along with the access code) are like your passport. You don’t have to show it every time you do something but you better have it handy if you have to prove your identity.

See also: 
What do I do if I lost the file with WM Keeper secret keys?
I lost the code to access the file with my keys.