Unlockables:

Muzak Remix
Beat Mega Man X3

Battle and Chase
Defeat Mega Man X1, Mega Man X2, and Mega Man X3.

Hint 1
You must unlock the fireball move and beat Mega Man X.

Hint 2
You have to beat Megaman X2.

Hint 3
Beat Mega Man X3

Staff
Unlock the fireball move and beat Mega Man X.

Dr. Wily
Finish Grand Prix mode with any racer.

Duo and the Hard Grandeur
Beat Dr.Wily three times and the Black Troop will challenge you. After winning each race, you'll have to find one of the secret parts before moving on.

Karaoke song
You must win one circuit without using any continues.

Images 1
You must beat Mega Man X6.

Images 4
You must beat Mega Man X6.

Images 5
Reach the gate's lab.

Images 6
You must beat Mega Man X5.

Images 7
You must beat Mega Man X2.

Images 8
Unlock the fireball move and Beat Mega Man X.