You can save laps under "options/save/save hotlap". It obvioulsy does not work with WinXP. Do a search on this forum (or the archive) to find more info on that topic.
For replays you can use a little tool called "GP3 Video v2.00" which can be downloaded here at [www.grandprix3.com].
This tool creates a new exe (works with no-cd patch) that lets you replay an unlimited amount of laps.
Be sure to mind the readme file that comes with it.