Netbook (Asus EEE PC 1000) as a GPS for North/Central/South America, and Europe

Hi everyone !

I recently bougt a netbook. I travel a lot around the world. I would like to use my netbook (Asus EEE PC 1000) as a GPS.

I live in Montreal, Canada, but I also travel a lot in Central and South America, as well as in Europe.

What is the best software to buy, to have access to map all over the world?

Seems to me that Garmin offers an easier access to map road for Europe at a more reasonable cost. I was first looking to buy Microsoft Streets & Trips 2009, but seems to cover only USA / Canada and parts of Mexico.

Should I go with Garmin or with Microsoft?

Thanks a lot for the advice ....
Joane