Ubuntu will run extremely slowly, if at all on that hardware. That machine needs a ram upgrade to say 256 though, then it will be fine for a very light window manager or command line operation as a lamp server.

In relation to your question, yes, you will have to partition your hard drive. Install windows FIRST and when partitioning, do not make the windows partition (c) the full size of the drive. The space left over can be used for linux. Most modern distrubutions can dual boot with windows very easialy and some include the facility to shrink the windows partitions of already installed systems.