I currently have a desktop with a single core AMD Athelon 2.08 GHZ, 1 GB ram running XP. I am planning on using an older laptop in its place. HP NC6400 Intel 1.6GHZ Centrino duo ,3 GB ram running Windows 7. Will I notice a slower performance with the laptop?
To answer your question, I don't see any reason why the laptop would be slower. The laptop has two times the CPU performance and three times the memory.
Intolerably would be a personal opinion that may not be shared by everyone. Let the one asking the questions decide for themselves what is intolerable.