What do i do if my sansa fuze won't turn on?

Make sure the battery is charged (hey, you never know). Try holding the "on" switch in "on" position for about 30 seconds. This should reset the device. Let go of the switch, then try powering on the player as usual. If it doesn't work the first time, try a few more times--I've heard it may take a few.

If that doesn't work, give Sandisk's tech support a call.