The whole thing is a bit tricky...
First of all Windows WILL work on every drive letter you install it so you
don't have to worry about chaning it for D: to C:
The problem is in your Program Files... every program installation uses
drive letters so if for example you have a game installed, it will only work
if it is beeing run from drive D:
There is where Partition Magic 8 comes
Theres a tool called DriveMapper or LetterMapper or something like this...
This tool will change all records of programs from a drive to another.
So the only thing you have to do is use a hard disk clone program like
Norton Ghost to copy files from partition D to partition C.
Also then you will have to use the recovery console from your windows xp cd
and run the commands:
fixboot
fixmbr
to recreate the boot files (since they will get erased from the hard disk
cloning)
Anyway as stated above the whole thing is very tricky and I don't recommend
it to novice users.
If you have any other questions please just reply.
George