Can people give a value out of 5 for likeliness that I cock something up by just popping in the disc and attempting to install W7.
It should work, according to
Microsoft released Windows 7 in October 2009. Now, more than a decade later, it’s being retired. Your Windows 7 PCs will keep working, but Microsoft is no longer issuing security patches as of January 14, 2020.
If you use Windows 7, you can still keep using it. Heck, you can even install Windows 7 on a new system. Windows Update will still download all the patches Microsoft released before ending support. Things will keep working on January 15, 2020 nearly the same as they did on January 13, 2020.