[ins0mnia24]

Your BCM is located on the passenger side behind your glove box.

A GM Tech 2 scanner ,Autotap and a few other common scanners have the ability to scan for BCM codes..
Those generic scanners that Autozone lets you use for free, to my knowledge do not have the ability to scan for BCM codes.

You can also run BCM diagnostic codes without a scanner by turning your key ON
Then OFF
Remove your radio fuse
Turn your key back to Accessories for 5 seconds and your BCM will beep
"The Beep is the same noise you hear when your lights are left on, Key is left in the ignition ect.. that sound comes out of your BCM."
After you hear it beep Turn the Key OFF
Then Immediately back to Accessories
The BCM will beep again followed by the Security Light on your Cluster
will start flashing the codes.
1 flash pause 2 flashes that is a code 12 which = BCM Diagnostic System Check
It will do that 3 times then it will start flashing out the BCM Trouble codes..

Sorry I do not have the actual codes Memorized to list them because there is specific codes for options like keyless entry and ect but that will get you started..

You can also take your dash apart so you can see the BCM
And look for a Dark blue wire going from the BCM to your Stereo that is what supplies power to your stereo you could always check the pin on that wire and see if it is loose on the BCM side.
I forget what color the power windows are.

But judging by what you are experiencing my guess is that you need a new BCM because that is what supplies the power to your stereo, interior lights and your power windows..
Use the parts numbers on the post I gave you the link for and see howmuch it costs at Gmpartsdirect.com
I think they run $150-350

But let me know how you make out electrical problems suck