Media sharing between Vista pc's

I have a couple of Vista pc's throughout the house. I have to do the
networking with wifi and there are a lot of access points in the area, so a
lot of fluctuations.
I share media (video, photo) from one machine and watch from other Vista
Media center Pc’s in the house. MC connects to a shared folder.
I’m trying to find out how to adjust the caching for especially video
playback. TweakMC has a setting for extenders. But what I’m looking for is PC
– PC
Thanks!

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Joel