Hello, 

I am making this post because the Microsoft employee I was talking to hasn't answered to my question and it's been about 2 weeks. So about one month ago I bought a new computer, on which I wanted to install Windows Movie Maker. Everything was doing okay until an error message popped up three times, saying "Windows couldn't complete the requested changes. The changes couldn't be completed. Please reboot your computer and try again. Error code: 0x800700C1". Then, another error message shows up saying that "Another program prevents the execution of the installation program from occuring. Error: 0x80070643. Source: Watson-x64".