I just upgraded to Windows 10 and then tried to install WIX and kept getting errors that .Net 3.5 wasn't installed and it has to be in order to install WIX. So I tried installing it and couldn't (I repeatedly got an error 0x800F081F). So I clicked on Help me fix this and that brought up an wizard that walked me through several steps none of which worked. Finally I figured out that I needed to reference the media with Windows 10 on it and then point to that using DISM, so I mounted the install .ISO file as my D: drive and then ran: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs and it finally worked!
I hope that I can save someone else the headaches that I had all day trying to fix this!