Rental Car from Austria/Germany to the East?

It depends of the car rental company.They have different policies for different countries.
In 2002 we rented a car from holland and I wasn't allowed to take to the East, particulary to Romania where we wanted to go.The car was from europcar.com
I think I saw a note once on one of the web sites stating that the car can't not be taken to Eastern Europe.
You have to call them up and make sure you are allowed to take the car to the East.

Depends on what's considered East. Eastern Europe was a Cold War term - sorry, Rick Steves - and Europeans don't call Czech Republic, Poland, Slovakia, Hungary Eastern anything (it's Central Europe). Check individual rental contracts for exclusions.

Actually we still call anything East of Bavaria Eastern Europe and so do car rental companies. Fact is you can rent any size car from any of the major car rental suppliers and take it into Eastern Europe - as long as you tell them upon pick-up of the car. In that case they don't hand you out a Mercedes, BMW, Volkswagen or Audi but rather give you a Ford, Opel, Asian car etc. You might also want to check with www.sixt.com...

Economycarrentals.com