The “KDE Wallet” is a password management system for your KDE desktop. It maintains lists of passwords for such things as Kmail, your IMAP email client connections for Thunderbird and the NetworkManager wireless login passwords.
Change into the directory /home/<user name>/.kde/share/apps/kwallet/ and delete the file kdewallet.kwl. This will delete the existing Wallet.
The next time you use a feature that requires the wallet you will be prompted for a new password as it creates a new wallet. You could also create a new wallet and set the password — after deleting the kdewallet.kwl file — using the wallet management tool. Start=>Applications=>System=>Wallet Management Tool. The KDE Wallet Manager then appears in the System Tray.
Open the Wallet Manager using the icon in the System Tray. Click on File=> New Wallet to create a new wallet.
Any time you create a new wallet you will have to allow applications access to the wallet contents the next time they are accessed.