Music, photos and videos can be played from standard USB mass storage devices, Xbox 360 proprietary storage devices (such as memory cards or Xbox 360 hard drives), and servers or computers with Windows Media Center or Windows XP with Service pack 2 or higher within the local-area network in streaming mode. As the Xbox 360 uses a modified version of the UPnP AV protocol, some alternative UPnP servers such as uShare (part of the GeeXboX project) and MythTV can also stream media to the Xbox 360, allowing for similar functionality from non-Windows servers. This is possible with video files up to HD-resolution and with several codecs (MPEG-2, MPEG-4, WMV) and container formats (WMV, MOV, TS).
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What PC operating system is required to stream content to a 360?
Windows XP with Service pack 2 or higher