Burnin' Rubber saves the game in C:\Users(yourname)\AppData\LocalLow\Adobe\Director 11\BurninRubber\Prefs

Delete, move or rename your existing file for a fresh start, the game only reads txt files with the name "xbrsaprog" as your savefile.

Other Xform games also use the LocalLow directory, this is good to remember as many of them don't have a reset progress button.