Hallo, newbie on this forum. Sounds like you're asking whether you can view movies on iTunes/AppleTV.
I once asked Seagate, which owns Maxtor why my Maxtor Shared Storage device would not show video. They explained to me that this is not a limitation of the device, but of how Apple has implemented DLNA on iTunes. My suspicion is that this was one of several conditions of iTunes selling Hollywood's content, but I don't know for sure. I suspect that the PC would have a couple of very fine bits of client software for DLNA, but iTunes isn't one of them. The AppleTV won't even stream music from an NAS
If you weren't referring to using iTunes, then I'm not sure what might be going wrong. I think you can use a player like VLC to open a particular file location, and that could be elsewhere on the network, but it's a little less convenient than using iTunes. My apologies if I've got the wrong end of the stick.