how can i fix my saxo?

i have a citreon saxo 1.4 west coast the other day i got in the cra n started it n there was no power steering the heaters wouldnt work the windows wouldnt work and the cd player wouldnt work then i revved the car and the battery light come on and the power steering come back then windows worked but not the cd player a few people have sed the alternator but iv changed it and i still have the same problem???????