If you need windows - you are much better off purchasing it.

Its a LOT less hassle and you get support to go along with it.

Considering that there is a lot of Freeware out there (enough that you really don’t have to purchase any other software beyond your OS these days …well …maybe Office as I’m not sure how good Open Office is in terms of compatibility) its worth the few $$$'s for a legit OS.

I know that in Australia if you do happen to be a student you can get discount prices on some Microsoft products though. Like really good prices. Worth looking into.

You do always have the option of installing a flavour of Linux however that could require a bit of learning.