The game appears to have quite a strong personality, since it does not like at all to be installed wherever you wish to – instead, you have to let it be installed in the standard location. In other words, when the MotoGP 08 InstallShield Wizard reaches the step labeled “Choose Destination Location”, the default installation directory will be displayed (“C:\Program Files\Capcom\MotoGP 08”). Select “Next” to continue to the next step. Do not press the “Change” button as that’s what causes the problems.
Capcom has been, as you see, prompt to offer the solution and the developers promise a free patch for MotoGP 08 to fix the problem and allow you install the game wherever you want to (and also be able to play it afterwards).