I get this question all the time…and found this to be the best way to just forward someone and get them out of your hair.
Now, it gets complicated when you factor in costs of memory and disk access. Generally, when a program needs to access information, it first loads it from the disk and then stores it in memory. From there, it fetches it again from memory until when you are finished, it saves it back to the disk. Fetching information from the disk is very slow, and from memory is still quite slow, when compared to the speed that the processor is running and doing work at. This is true even for your older CPU. If a program is running slow, it is very important to determine if it is slow because the CPU is busy doing work, or if it is slow and the CPU is idle waiting for information to load.