Yeah its all in the upgrades.
The CPU may still be willing but that 4200rpm IDE drive will have to go and the choices are getting limited.
What I really love doing at the moment is when I get a customers laptop in that has a single core Celeron in it.
You can pick up a 2Ghz dual core C2D for around a tenner, swap that in and you then have a customer for life. Often I don't charge them for it or just charge them the tenner. However, the improvement is so much they rave about it and refer you on to others. Its a worthwhile investment.
Only problem is I'm stuck with a pile of Celerons......