The example of computer is valid if you understand one thing here as below.
Yes people may use older versions of windows to get by doing some functions, but with the improved windows version you may be able to use newer softwares/hardwares etc. better to be successful.
Hence the improvement (islam) helps achieve salvation. And older religions NOW are not to be followed despite older religions still are considered valid if found.
In short, being non-functional/obsolete does not mean invalid.