video files

Hey guys, I'm running a little low on memory space in my computer, and I want to buy an external hard drive but until then I need to delete some files. I have a few old video files still saved on my computer and I'm wondering is this even necessary? Once you upload your video to YouTube...

Can anyone please tell me why any video I record using my iPhone cant be used in Windows Movie Maker? :P After I record it, send it to my laptop, then go to add the video file to WMM and it says I cant :P Im pretty sure I used to use iPhone videos on WMM a while ago. :P