Bob, I suggest you do NOT install the Linux boot loader (Lilo or Grub) in the main partition or you'll replace the Windows boot loader.
I suggest, you resize your partition: with 6 Gb for Linux is more than enough and you can create a third partition for Home (Linux). Then you can have the operational system files of Linux in the second partition and your files and data (Home) in the third. For the boot Linux partition (\) 6 Gb and for the \Home 8-15 Gb should be enough.
Then you can install Linux by the 'alternate ISO' download (not the common one). Choose not to install the boot loader in the main boot sector but rather in the boot sector of the second partition (this should remain an inactive partition).
Use Bootpart to add an entry for Linux in the Windows boot loader (
http://www.winimage.com/bootpart.htm).
Be happy