yes you can install ubuntu without losing your data - and you can keep vista on it too - it can be setup for dual boot, meaning you can choose which operating system you want to boot into when you use it at any given time.
not sure about picasa but no google chrome for ubuntu yet - however firefox works great with it.
I can install this all for you and set it up to see if you like it
give me a call this week and we'll go over everything including your other work
- shoot me an email davburr@yahoo.com