back´-up, noun
1a. A copy of computer data on storage media, which can be restored in case of system failure.
1b. That which everyone recommends, but hardly anyone does.

QTParted can resize NTFS partitions. Make a backup, though, just in case something bad happens.

If you don't intend to install Linux, you could create a FAT32 partition at the end of your NTFS partition. Knoppix can create a persistent home image on a FAT32 partition just fine, and you could still use the rest of the partition's space from within Windows (something you can't do if you format it as ext2/ext3).

More notes about Knoppix 3.8:
- In previous versions of Knoppix (e.g. 3.3 and 3.4), you'd use a cheatcode similar to home=/dev/hda2/knoppix.img, but in 3.8 you have to use mnt instead of dev.

- Persistent home works fine off of a USB thumbdrive ("home=/mnt/uba1/knoppix.img")

- Knoppix 3.8 is having problems unmounting the persistent home partition cleanly and shutting down on the two computers I've tried it with. Leads to a few inode errors on the next boot.