It's got Windows 2000 Pro and PenX installed, but on a Celeron 500 that's going to be a bit clunky. So...
Step 1: Image the disk so I don't lose the install that's there.
Step 2: Set up a floppy with Smart BootManager
Step 3: Install Ubuntu Linux (alternate). I'm waffling on this, though. It might be a good choice to go with Xubuntu, as it's system requirements are a bit lighter.
Step 4: Install fpit and configure it for the Stylistic 3500 digitizer.
Step 5: Try out various linux tablet utilities
Step 6: Find and try out some slide-show and media player utilities.