You can configure Vista to automatically clear the page file (cache) at shutdown:
- Click on Start > Run > type regedit
- Go to:
- HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Memory Management
- In the right pane, locate a key named "ClearPageFileAtShutdown". Double-click on it and set its value to 1. From now on each time you shut down Vista the cache is automatically cleared.