It's amazing that the Microsoft fan base still chant the same mantra:
Most small businesses still need a Windows server to be the foundation for their file and printer sharing.. not all.. but many do.
So why do you need Windows if you want File and print sharing? That's as dumb as saying you need Microsoft Office if you want a spreadsheet or Word Processor.
For File and Print you can use Lotus Foundations Server or Linux with CUPS.
For spreadsheet / Word Processing you can use Lotus Symphony or Open Office.
All without paying any money to Microsoft.