I use Windows7 occasionally, but don't recall hearing of this happening. I don't really see that Widows itself should be uninstalling or deleting Firefox. Are you talking about the process of upgrading Windows from say Vista to Win7 (If indeed that example is possible, with free Win10 about to be offered to existing users and the numbering system disappearing ) You appear to have posted using Fx37 on Windows 7 so I hope you got it sorted out. It's also worth notingFx38 is now out so you should be updating Firefox