What it is
Active Setup is how a machine-level installer performs per-user initialization: entry under HKLM\…\Active Setup\Installed Components with a StubPath and Version; the first time each user signs in, Explorer runs the stub once, then writes a mirror stamp under that user's HKCU. Later sign-ins skip it because the user's stamp says “done, at this version.”
HKLM\…\Installed Components\{GUID}
The machine declares the stub (admin to write)
HKCU\…\Installed Components\{GUID}
Your stamp proves it ran for you; bump
Version machine-side and it re-runs for everyoneWhy it matters to tuning
- Not a startup entry: it won't appear with the Run keys. A once-per-user thing that keeps running is often here, not in Startup.
- Version bump = re-run for all users: some updaters abuse this to resurrect per-user integrations you removed.
- First-sign-in freezes: a broken stub hangs the whole post-logon shell. If first logon after an install stalls on one account only, check the HKCU stamp — is it present?
Audit rule: deleting the user's stamp forces one more run; deleting the machine's key requires admin rights. As always with machine scope, the read is free and safe — the write is what you need to be sure about.
ProofTune ProjectEngineering notes — every claim here names the bytes a real tool touches. Verify first, install second.