Cheers for the advice guys...as usual its made to sound soooo easy!
Well, I'm gonna have a stab after i finished work tonight.
So...summing up the above (please correct of wrong!):
Turn off PC
Remove old drive (noting cables etc)
Install new drive noting master/slave settings/cables etc.
Turn on PC
Now...at this point it becomes a little confusing for me. Will BIOS start automatically or do I still have to hit Delete?
When you mention 'boot from the CD'..uhm...which CD is this exactly, the Windows XP CD or should I have something else ready?