Windows 95 defenses against installers that overwrite a file with an older one (devblogs.microsoft.com)

Raymond Chen explains how 16-bit Windows guidance expected installers to compare file versions and only overwrite system components with newer builds. Because many installers ignored that and overwrote newer Windows 95 files with older Windows 3.1 ones, Windows 95 added a repair mechanism: it stored backup copies of commonly overwritten files in SYSBCKUP and, after an installer ran, restored the higher-version copy. Chen notes that earlier approaches that simply blocked overwrites often caused installers to fail or fall back to reboot-and-retry tactics, so the post-install cleanup strategy worked best.