Ken, why not use a NAS with a media server (like the WD solution Chris pointed out)? Or just map a network drive if you don't want to fiddle with media servers. I have a mixed WXP and Mac environment at home and it works quite well with my NAS. I use a combination of mapped drives for windows and media server for the PS3.
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Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1