Update: If you are looking for support of ext2 or ext3 on Vista read: Access your Linux partition from Vista, but if you are looking for ext2 or ext3 from XP, continue reading.
The software we are going to use is Ext2IFS and can be downloaded from its home page Once downloaded install it on your Windows system on your dual boot PC.
Enable large file feature, and select a letter for your linux partition, you better leave untouched the swap, specially if it is a laptop and you do suspend to the swap
Click on finish and reboot, that is all.
Here you can see how the linux file system is available for windows, and how i am copying a file from windows to the Linux partition.
In this screenshots you can see the file that was copied from the windows to the Linux using the Linux file explorer (Nautilus)
As you can see the file permissions were assigned according to the directory owner.