Getting 4gb of ram so thought I'd better go 64bit.
Haven't done windows yet but I thought i'd start with Kubuntu.
http://ubuntuforums.org/showthread.php?t=41865
I did what jdong suggested by typing
sudo dpkg --get-selections > selections.txt
Copied my home dir to another partition.
installed ubuntu64 (yes I downloaded the wrong cd

)
Copied my Home dir back.
ran the following commands
sudo dpkg --set-selections < selections.txt
sudo apt-get dselect-upgrade
Only thing I had to do otherwise was recompile the themes I had sert since they were compiled for the 32bit version but that was a simple case of going into the folder (lucky i still had the downloads, running the following
make clean
./configure
make
make install
)
Voilla done... Only thing is I now have gnome and related apps where I forgot to select Kubuntu before starting the download