Hi,

If windows XP pro installed on a G: drive does that matter or should it be installed a C: drive?  If I want to change it will I need to repair XP Installation or re-install it from scratch?

The drive letter doesn't really make a difference. The only problem I could see is that when you install programs to the G: drive, it may install to the C: (if you have one). If you don't have a C:, then G: will become your default.
If you wanted to change it, I think you would need to reinstall it from scratch.

Ok thanks

Actually,  that you can change your drive letter, but then, most of your programs won't work because when they are installed, some of them usually put on the registry the location of where they were installed, and that would be pointing on G:...

Some badly coded programs might require files from windows/system folders and could be hardcoded to look for them on C: (maybe?).

So I will need to do a complete re-install to fix it right?

Just leave it the way it is.  There is nothing special about the C: drive, other than traditionally, that is how the first (and typically only) hard drive has been enumerated by DOS and legacy Windows.

To "fix" this non-problem, you would have to either reinstall Windows, or change the drive letter assignment and modify a zillion registry and configuration file references.  There are some third party programs that purport to do this for you, but I wouldn't trust them very much.