For whatever reason, my recent test-sampling of public domain films on this website with windows 8 revealed an error/no-play/corrupted file prompt for the mp4 films which format is more than sufficient for films of that genre/time period; and hence, easy on memory/hard drive space. The mp4 format is not brain surgery and one may only surmise that, in a manner consistent with that 'brilliant planned obsolescence strategy' that worked so well for GM (Hmmmm! Riiiiight! ), hopes were leaping for unnecessary, redundant trips to the app store to which one's directed would be the outcome (hmmmmm!). I recommend the following though I'm sure there are many other free apps available to play mp4 files, etc. ... :
Windows XP, Vista(32/64bit), 7(32/64bit)
Built-in Codecs & Online Codec Center
ALShow includes the basic codecs to play most of the movies. For those rare kinds of codecs that are not popularly used, ALShow will download the codec from ALShow Codec Center then install it for you. With ALShow, you do not have to wander around the internet to find the proper codec for your video. ALShow will do everything for you.
More than just a movie player, ALShow has the function to capture audio, video or screen shots to your hard drive.
3G2, 3GP, 3GP2, 3GPP, ASF, ASK, ASX, AVI, BMK, DAT, DIVX, FLV, IFO, K3G, M1V, M2T, M2TS, M2V, M4V, MKA, MKV, MOV, MP4, MPA, MPE, MPEG, MPG, MTS, OGM, RM, RMVB, SKM, SMI, SMIL, SRT, SUB, SWF, TP, TS, VOB, WM, WMP, WMV, WMX, WVX