HP iPAQ hw6510 / hw6515

Hi, Although I am very computer-literate with PCs and Windows, I have no clue what this phone is capable of. I am thinking of purchasing one, but what type of applications can it handle? Can it hold Microsoft Word for typing documents, or can any other Windows software be loaded onto it? And if so, what are it's limitations on size of software that can be loaded onto it?

Thank you.