// user-function to include in your script
// deletes all other contents of any type except the script itself
delete_all_other_contents()
{
    string thisScript = "name of notecard not to delete";
    string inventoryItemName;

    integer index = llGetInventoryNumber(INVENTORY_NOTECARD);
    while (index)
    {
        --index;        // (faster than index--;)

        inventoryItemName = llGetInventoryName(INVENTORY_NOTECARD, index);

        if (inventoryItemName != thisScript)
            llRemoveInventory(inventoryItemName);
    }
}

default
{
    state_entry()
    {
        delete_all_other_contents();
    }
}