Starting from version 0.1.0 up to 0.1.5 the bitcoin software could be run only on only Windows 2000 / Windows NT and Windows XP
Was there a technical reason from Satoshi for this choice of operating system, or maybe he wanted his client to be run on the maximum amount of computer, or maybe he had more knowledge of windows ? Linux seem more fit for open source and "Cypherpunk" that windows.