Movie Maker Glitches

OK, Let me get one thing straight off the bat, i dont doubt any computers or softwares ability to handle hi-def files. there we go, now heres my question/dilemna that i'd like an answer to: I have a capture card called an elgato hd60 pro, if you dont know what it is, go look it up! its really cool, and its well worth the money, BUT! recently movie maker has been giving me alot of bullcrap, one of the most recent issues ive been having is, that moviemaker doesnt even accept my files, Theres a setting on the elgato software that allows me to convert the file into certain resolutions and file types depending on the the software or hardware the files going to, for example, elgato can convert the file into a movie maker file, i forgot what the codec is thats specifically for movie maker i think its .wmlp. but thats not the point, i have a 20 minute long 1080p60fps video, something much shorter then i normally do, so i expect it to work but instead it straight up says its "corrupted" before even processing it... it really **** me off! this is the first time its done this to me, and i have no idea whats going on, somebody help me... plz