noob help :?

[turbinater]

is it safe for me to use Knoppix?

Yes, it's perfectluy safe.

what can and can't I do without causing any damage? will just trying to access the data on my HD do any harm?

Anything you do shouldn't cause any damage to your hard drive, unless you try to repartition it. Your hard drive probably wont even be mounted while you're playing on the cd.

or do I really need to repartition before I get going?

You only need to repartition if you're going to install knoppix to your hard drive.