blue4u
I posted this here before and will do so again for you and hope no one gets upset with me for repeating myself.
http://www.ableton.com/forum/viewtopic.php?t=44053&highlight=vst+rewire+slave+modeCheck the archives here and also type in ReWire in Google.
Go to Propellerheads site too as ReWire is their "baby" so to speak
As said before, ReWire is not that big a deal to understand as it operates by the order in which you launch the applications. If you have RiffWorks open and launch Reason or Ableton they are forced into ReWire slave modes, period.
The bigger deal will be just understanding the software programs you are using in the first place.
Rotsa Ruck on all this