1. In the bottom left corner of the screen, click the "START" button, then click the "Run..." icon
2. After the dialog box opens, type the command "control keymgr.dll" (without quotes) and click OK (see Fig.1)
   
   
3. In the newly opened dialog window, click once on the line with the label "*.prfuk.natur.cuni.cz" and then press the "PROPERTIES" button.
4. In the next window, click the "Change" button (located in the bottom right corner) (see Fig.2)
   
   
5. Enter your old password and then your new password. Type the new password again into the last field to confirm the change. (see Fig.3)
   
   
   
   
6. Then press OK and close all dialog windows.