I don't know if anyone knows how to fix this, but recently I had to reinstall my copy of windows. After installing the driver for my sound card, suddenly my taskbar disappeared. It seems it is still down there (tweaking the settings sometimes shows a HINT of it that I can right click on), but nothing I do will make it come back to normal.
Well it's Vista, but much faster and cleaned up a bunch. Some nice new features in there. The reviews are MUCH more positive than when Vista was coming out, that's for sure. As for upgrading, the system requirements are pretty much the same.