You can't.
.sps and .xps files are just code that the PS2 uses in GT3 to replay your lap in replay theatre.
To use them you need an x-port or sharkport to load them onto your memory card so you can view them in the replay theatre on your PS2.
Though if you found a PS2 emulator, had a GT3 image to play in the emulator you theoretically could view them on a PC view the emulator if your emulator as a virtual memory card (or some such thing to load files into games). That should work but I am not aware of anyone ever doing that.
