Back up

I?m looking for a best solution for backuping data on computer. I have tried the Acronis TrueImage but it has not satisfied me. I have such problem two computers and a have to crossover back up them and if one goes down and i replace it with new one. The new one has to booth all the data form computer that is not down. And it has to have possibility to recover the new comp that is empty thru PXE Boot functionality.