My computer is running on a 1.7 GHz celeron processor. It also has a graphics card which is slightly under average by todays standards. I can run some games alright, but when I need to use it for more demanding games it falters. I also want the computer to run faster on the desktop when listening to music etc. So I thought that buying a new cpu would be the best bet to speed it up. Would it make a big difference to both things if I bought a 2.8GHz P4?
It is best to take a balanced apporach to these things, otherwise all you do is move the bottleneck from one part of your system to another.
Please provide more information. What graphics card are you currently running ? What games specifically do you want to play ? How much memory do you have, what type? What is your operating system ? What type of hard disk are you using ?
Your processor is a cut-down version of a P4, but should be more than adequate for listing to music whilst working.
In general, for gaming, the graphics card is a critical component and will, to some degree, make up for a slower processor.
For general windows work, the graphics card is less important but the amount of free physical memory is paramount.
For number crunching, you need to ditch the Celeron and get a full P4.
The speed of the hard disk and amount of free RAM will affect the speed of applications loading.