Error 5 in a service context means the account starting the service, or the account the service runs under, does not have permission to do something the startup needs. That can be the service binary, its registry keys, or the logon itself.
sc qc and the service name, open Properties, Security, and confirm the service account and SYSTEM have Read and Execute permission.If the error only appears for one service, the problem is usually that service's own files or account. If it appears for every service, check whether the account you are signed in with still has administrator rights, and run sfc /scannow in an admin Command Prompt.
Does error 5 always mean I need to be an administrator? Not always. Starting a service needs administrator rights, but the error can also come from the service account lacking permission on its own files, even when you are an administrator.
How is service error 5 different from a file access denied error? The code is the same, but the context is different. Here the denied access happens while Windows starts a service, so the fix is in the service account, its file permissions, or its registry key, not in the file you were opening.