I've just installed Leopard 10.5.1 and it seems a bit slow. e.g. Help is REALLY slow. Any advice on how best to upgrade? More memory? If so, what's best? ... and where to buy? Here's my System Profiler detail: Model Name: PowerBook G4 15" Model Identifier: PowerBook5,6 Processor Name: PowerPC G4 (1.2) Processor Speed: 1.67 GHz Number Of CPUs: 1 L2 Cache (per CPU): 512 KB Memory: 512 MB Bus Speed: 167 MHz Boot ROM Version: 4.9.1f1 Advice welcome.