How can you tell if you computer is bad, I have an 00 929. also does anybody know exactly what the ecm controls ??

 

Easy way is to put it into another bike and see if its doing the same thing.
If you dont have a spare 929 kickin around, then you would need to figure out what it is that isnt happening and weather or not that is controlled by the ECU.

In short, the ECU controls the Following.
Ignition Timing/Advance
Fuel Delivery through the injectors, injector pulses
And It outputs the Tach signal to the instrument cluster.

It gets its inputs from sensors on the bike, TPS, ECT, Ignition pulse Generator, Cam position sensor,Map sensor, IAT Sensor, and a few others.
If any of these fail, you get a trouble code, or a no start condition, or both.

 

where exactly is this on the bike is my question

 

Under the seat, next to the battery. You will need to take off the bracket for the fuel tank/seat hook to get the cover off and remove it.