Pop the hard drive into your Windows machine. Format the drive as FAT32 using your Windows machine (right-click on the drive, select "Format").
Now the hard drive can be read and written on both the Mac and your Windows machine.
FAT32 format has a number of limitations including file name lengths, characters that can be used in filenames, and the size of the files themselves (as artov said, no file can exceed 4GB in size).
Why not simply network the two computers together, either via wireless or a wired connection, and copy the files between the computers like that?