Windows 10 Programs will not start with a functional Win10 ...

Quick checks to narrow it down​

• If they open via full path but not from desktop/taskbar/Start: your .lnk (shortcut) association is likely broken.
• If they do not open even via full path: something is blocking launches (policy/AV/registry), or system files are damaged.

If shortcuts are broken (lnk fix)​

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.lnk]
@="lnkfile"

[HKEY_CLASSES_ROOT\lnkfile]
@="Shortcut"
"EditFlags"=dword:00000001
"IsShortcut"=""

[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.lnk]

If apps won’t start even by full path​

• Run regedit and browse to:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
  If you see subkeys like firefox.exe, chrome.exe, excel.exe, winword.exe with a value named Debugger, delete those subkeys (only those), then reboot.
  4) New test user: Settings → Accounts → Family & other users → Add someone else to this PC. Sign into the new profile and try launching the apps. If they work there, the issue is profile‑specific (we can reset associations and startup entries in your main profile).

Two quick questions​

• Did this start right after a Windows Update or installing/uninstalling security software? If so, which and on what date?
• What exactly happens with Win+R notepad and with running the full .exe paths above?

• Run regedit and browse to:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
  If you see subkeys like firefox.exe, chrome.exe, excel.exe, winword.exe with a value named Debugger, delete those subkeys (only those), then reboot.

• CCleaner’s “Smart Cleaning/monitoring” can register itself as a Debugger under Image File Execution Options. That forces launches of app.exe (chrome.exe, excel.exe, etc.) to be intercepted or redirected, which makes programs fail to open when the Debugger path is broken or blocked. Removing those IFEO subkeys (and then uninstalling CCleaner) clears the launch hook.

• Check there are no leftover Debugger hooks:
  PowerShell (Run as admin):
  Get-ChildItem 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options' |
  Where-Object { (Get-ItemProperty $.PsPath -ErrorAction SilentlyContinue).Debugger } |
  Select PSChildName, @{n='Debugger';e={(Get-ItemProperty $.PsPath).Debugger}}
  If this returns nothing, you’re clear.
• Optional: Task Scheduler → Task Scheduler Library → remove any CCleaner tasks if present, and Task Manager → Startup tab → ensure no CCleaner entries remain.
• Going forward: I’d avoid registry/system “cleaners.” Windows’ built‑ins (Storage Sense, Disk Cleanup, Reset this PC) are safer and won’t hook IFEO.