Avis - one way rentals in Europe

I'm planning a trip Eastern Europe and the Baltics and was wondering if it's possible to rent a car in let's say Vienna and drive it up Tallinn or Riga, one way?
The folks at the 800 number haven't been very helpful.

Also, last time I rented a car there with Avis they would charge extra for each country visited outside the rented country. Do they even allow you to drive outside EU countries, like the Ukraine and Russia?

There is usually a frighteningly large fee to do this - you are effectively charged the full cost of repatriating the vehicle back to the country that the vehicle is registered in. Vehicles can be freely driven across borders in the EU, but if the vehicle stays permentanty in a different company then it has to be re-registered. That's why you'll be charged the repatriation fee.

Hertz operate the transfer desk ( http://www.hertz-transfer.eu/ ) which shows which vehicles are "wrong country - need to go home", and hence you don't get a painful surcharge if you return the vehicle to where it needs to be. But these are for immediate rentals - you can't reserve ahead on these.

thats what i figured... also it's one thing to drive across EU countries... those in the Schengen area obviously don't have border controls... but it's another thing to be insured. Not sure if this is the case anymore but many Avis outlets wouldn't let you drive to certain countries.