the x.264 (non 720p) ones, will be .mp4. Not sure why your machine isn't showing the extensions, they do on mine.
I run haalia media splitter which will play these. And you need an h.264 decoder. Windows 7 has one built in. And older version I'm not sure what you'd have to install.
AMD FM1 x4 A8-3870 Llano, Gigabyte GA-A75-D3H, 4 Gb DDR3 Ram, Seagate 500 Gb, Seagate 1500 Gb, HVR3000 x 2 (DVB-S), Nova-T 500 (DVB-T), USB-Uirt, SPDIF -> Yamaha RX-V540, ATI HD6550 (OnBoard) > Samsung LA46A650 TV (HDMI), Harmony Remote 525
Windows 7 Ultimate x64 SP1, NPVR 2.4.3, AC3Filter, 1 x Popcorn Hour A-100, 1 x AppleTV with Plex