You are encouraged to partition with Linux. It depends on your needs, but for a strictly surfing/work PC on that size hard drive I would suggest 5-10GB for /, 512MB for swp and the balance given to /home. Further partitioning isn't really necessary for desktop use. Some servers isolate parts of the filesystem as partitions for various reasons but for your purposes you will do fine with separate root and home partitions. The other advantage is that with separate root and home partitions, you can reinstall Ubuntu without losing data (and I guarantee that if you like to mess around, you will eventually break it so badly that you will just reinstall, although Linux is generally repairable from almost any state to a guru) and also try out multiple distros and share the home between them.
For an analogy: / is like C:\, /home is like My Documents. Kinda.
XFCE is cool. Snappy, too. Windows does feel faster than KDE or Gnome, it has to be said.