I *had* been leaning heavily towards Knoppix, mostly because it has a good "live CD" implementation and was among the first to support NTFS, which is the file system I use in Windows XT. My recent research pointed out that Ubuntu is the most popular Linux Distro(bution) and has built in NTFS support. It is also easier to install on the hard drive compared to knoppix which is (apparently) better suited for use as a "live disk", where it is run from the CD and does not use the hard drive.
To Summarize, Ubuntu:
Is Popular -and-
has a correspondingly large pool of Community Support.