how much RAM do I need to run windows through paralells sucessfully/smoothly?

You didn't mention which version of Windows the program requires, or which MacBook Pro model you have.

I have successfully run Windows Microsoft Office 2010 and other older Windows applications under both XP and WIndows 7 with Parallels 5 in 2Gb of total RAM on my mid 2007 MacBook 2,1 with integrated GMA 950 video on both Mac OS X 10.5.8 'Leopard' (though Win 7 is not 'officially supported') and 10.6.6 'Snow Leopard'

But performance is, uh, 'limited', especially for processor-intensive applications like graphics programs.

My Core2Duo 2.16Ghz processor often runs at 100% of one processor, so the fan is often running at high speed all the time Windows is running. It is still possible to run Mac applications like Mail and Safari at the same time.

Since I upgraded to 4Gb RAM (although by design, my Mac 2,1 system only recognizes 3Gb) Windows 7 runs a bit better, though still at a slower speed than the same program with Windows 7 under Boot Camp where it has access to the full 3Gb.

I do own a copy of Parallels 6, purported to provide some performance gains, but I have not yet installed it, because I doubt that my current configuration will provide enough performance gains to warrant the time and trouble to install Parallels 6 and then have to once again deal with Microsoft Support over yet another 'reinstallation' of my perfectly legitimate, legal copy of Windows 7 Home Premium.

If you don't need simultaneous access to both Windows and Mac applications, Boot Camp will likely give you adequate performance with XP in 2Gb. RAM memory upgrades are certainly available from Apple and reliable vendors such as Other World Computing (www.macsales.com) where I've purchased several of my RAM and hard drive upgrades for a MacBook and a MacBook Pro.

Message was edited by: kostby