“There was a problem starting…”
A RunDLL box on login is not really a missing-file problem. Something is still being told to load a DLL that is gone, and nothing on the machine needs that file any more. What has to go is the instruction, not the absence.
What is happening
Windows has a small launcher, rundll32.exe, whose job is to run one function inside a DLL. Plenty of legitimate software uses it for background tasks and registers an autostart entry pointing at its own library.
When that software is removed, the file goes and the entry sometimes stays. Every login, Windows dutifully follows the instruction, finds nothing, and shows you the box. The error is a leftover, which is why it appears at a fixed moment and why nothing else seems broken.
The second common origin is the one worth being careful about: security software deleted the file because it did not like it, and left the autostart entry behind. In that case the message is a record of something that was removed on purpose.
Do not download the file it names
Searching the DLL name from the message leads straight to sites offering that exact file, and here the usual advice is not merely useless but backwards. If an antivirus removed the original, putting a copy back is undoing the removal, and you would be trusting a stranger to hand you the file your security software objected to. The message goes away either way, which is what makes it convincing and what makes it dangerous.
How to fix it
- 01Read the message and write down the DLL name and the path. Both are the evidence: the folder it points at usually names the program that left it behind.
- 02Open Task Scheduler and look for a task that runs rundll32.exe with that file. Leftover update tasks from uninstalled software are the most common single cause.
- 03Check the startup entries. Task Manager’s Startup tab shows some of them, but the registry Run and RunOnce keys under HKCU and HKLM hold more, and 32-bit entries hide under the Wow6432Node branch of the same path.
- 04Use Autoruns if you want all of them at once. It lists every autostart location Windows has and highlights entries whose file no longer exists, which is exactly what you are hunting.
- 05Delete the entry, not the file. There is no file to delete, and that is the point.
- 06Reboot and confirm the message is gone. If it returns, something is putting the entry back and that is a different problem worth taking seriously.
Autoruns is Microsoft's own tool for step four and it is free: the official download and its SHA-256 are on its page here, which matters for a utility that people habitually fetch from wherever a forum post pointed them.
Is rundll32.exe itself a problem?
No. It is an ordinary part of Windows and it lives in System32. Its name turns up in these messages because it is the thing doing the loading, not because it is the thing at fault.
It is true that malware has made use of it, for the same reason it uses other built-in tools: a legitimate signed program running a library draws less attention than an unknown executable. That is a reason to read which file is being loaded and from where, not a reason to distrust rundll32 on sight. A copy of it anywhere other than System32 or SysWOW64 is a different matter.
If the file really is needed
A RunDLL box at login is a leftover, but a program failing at launch with a missing DLL is a genuine gap. Look up the file named in your error to see which runtime package contains it, with the publisher's own URL and its SHA-256. And if the file is present but Windows still complains, an entry point error is a different problem again.