I think you've got 1GB RAM in there, right? I'd be tempted to pop another 1GB in there and see if that automagically fixes everything up for you: it'll push the system from just below the sweet spot for XP to just above the sweet spot. I've no idea how easy it is to add memory to an N100, though. You're stuck with the integrated video and the unnecessarily slow hard drive that Toshiba choose to use.
You can also turn down the "fancy" transitions in the UI, but I'd add the memory as the first step.
Your cheapo netbook has roughly the same specs as my numbingly-expensive 4-year-old notebook, and I watch videos just fine at 1080p after adding RAM and a faster hard drive.