Was running 10.4.10 with no problems at all. Bought a separate HD and backup up system using Super Duper. Discovered Leopard was v v flaky so reverted back to Tiger. Now if I try and launch 'software update' by using the Apple icon in the top left hand of the screen it wont launch anymore. If I then try to launch by clicking 'About this Mac' and then clicking the pane 'software update' it launches one of my pictures from iPhoto rather than the updater!! This is after repairing permissions... Any ideas anybody, please!!... Leopard really seems to have messed my Mac up. BTW am running a Power Mac dual 2GHz.