One possible, in boinc manager > options > general > run the client should be ticked. The other in services.ms, if installed as service, check if boinc is set with startup type to run automatically or manual (somewhere in there's an option 'automatic, delayed start' too, which speeds up booting).

Untick, save, tick, save. Nothing cryptic. If you've not installed as a service, BOINC always runs signed in or not when you did, than it's not there. Don't know if WCG in their custom kit wisdom renamed the service moniker, i.e. under W in the sort order instead of B.

Still no success, check Task Manager > Startup to see if BOINC is listed. More self help at https://www.howto-connect.com/windows-10-run-program-automatically-at-startup/

There's a LOT about this that's cryptic... To begin with, I've always just grabbed the installer and run the default install, so whatever that installs is what I normally have installed.
1. From where I'm sitting, I must have the necessary files installed because when I manually start the Boinc Manager after Windows starts up, it then continues to run normally as before i.e. after the 3 minute wait, it will start the screensaver. So I can't be missing files.
2. After system startup, there are no Boinc or WCG processes to be seen in the Windows process monitor. They are also not lister under Startup processes. Once I start up Boinc Manager once, the Boinc client process is there under processes.
3. I have tried manually (one by one) to add the various exe files in the Boinc directory to Startup. The only one which seems to produce half a result is if I add boincmgr.exe. However, as a fix that isn't entirely satisfactory because it actually opens the manager window at startup and I have to click it away. Which is a minor annoyance given that in the past it just fired up in the background.

Given I have not played around with any Boinc settings for ages and haven't fiddled with any other system settings recently either, I suspect Microsoft has once again broken something during an update that somehow wiped the Boinc settings or somehow prevents them from being installed on certain systems. Maybe it's having one of its periodic fights with Nvidia graphics cards, I don't know, I'm not a developer. But if I uninstall Boinc and re-install it and it's still not working, I suspect there's something Boinc has to fix.

@Akerbeltz


The "/s" flag on boincmgr.exe means "System Tray" only, which means it fires up in the background.

If you're comfortable with the Registry, open "regedit" as an Administrator and make sure

Path:
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

Name: boincmgr
Type: REG_SZ
Data: "C:\Program Files\BOINC\boincmgr.exe" /a /s

Name: boinctray
Type: REG_SZ
Data: "C:\Program Files\BOINC\boinctray.exe"

Note: I don't know if the WCG customized version of BOINC uses a different path or different exe names. Change the above two keys as needed.

Once those are added in the registry, you'll also see them in Task Manager --> Startup tab in Windows 10.

Reboot and see if that fixes things.






If it doesn't fix things, you can try to download the WCG installer again and run "Repair" and see if that repairs anything that's missing.

If that doesn't work, run the same installer again and "Uninstall." Then reboot. Then "Install" then reboot.

Have fun! (Sarcasm)
Good luck! (Not sarcasm)

1 Downloaded Installer
2 Uninstalled via Installer
3 Rebooted
4 Manually deleted all Boinc/WCG folders
5 Ran CCleaner to make sure there was nothing "left"
6 Re-installed with default settings and rebooted
7 Seems to be back to normal

When I originally uninstalled, I did it via the Windows control panel, so there must be something left behind by that which clashes with re-install of WCG.

Incidentally, there are still no Boinc/WCG processes under Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run (I got 2 Adobe, 1 Realtek and Windows Defender in there). So wherever startup is defined for WCG, it doesn't seem to be there.

But thank you nonetheless for your help!