Ive used many software packages including the ones that cost thousands, and for the joe public, and even more, id highly recomend sketchup.
There where many issues with SketchUp and Vista, i did get it working eventually.. then they issued a patch fixing it.. and it went crazy again.. thankfully its sorted and should work fine now!
some graphics cards still have troubles, but for help with that see the support on the sketchup page.
For free software you cant beat it, and if there is someone willing to go one step further, you can download Kerkythea which is a free rendering package (makes extra swanky models in sketchup look even better and also let you place true lighting effects)
http://www.kerkythea.net/joomla/
You will also need the exporter to get the file format from sketchup to KT :
http://www.kerkythea.net/joomla/index.php?option=com_remository&Itemid=42&func=select&id=7
Happy Modeling!!