Voltage regulators are the best way to go when you want to use 110v devices on 220v systems and vice versa (http://www.nipponamerica.com/catalogue/jpg_NA-305.htm). They are more robust than transformers and protect the devices against power surges and dips. Also, transformers usually don't adjust the frequency, which is a big problem for motorized devices but normally not for hair flatteners. Unfortunately regulators are too heavy for traveling, I have a few 1000 watt regulators that weigth 12 to 15 kg each.

Argentina has a 220v, 50 hertz system. That's the same as most of Europe, the US is 110v 60 hertz. Read the labels on the one you bought in Vienna, I bet its 220 or 230 volts, 50 hertz, if that's the case all you need is a sturdy adapter not a transformer.

Here's a good URL for travelers to help them figure out what sockets and voltage they'll be facing on the road: http://www.voltagevalet.com/country/all.html.