This file has been reported to be part of a spyware/malware/trojan. It is likely that the problem you are experiencing is linked directly to the spyware/malware/trojan rather than an actual missing DLL-file and the recommended course of action is to first locate/remove the Malware. We do not recommend downloading this file.
DLL-Files.com Support says:
This is a possible manual solution for you 'handyman-fixers' out there:
WARNING: Do this at your own risk. manually changing the registry could cause system critical errors if done incorrectly, the instructions below are not guaranteed to work on your particular system setup.
At the taskbar, click Start|Run. Type 'Regedit' and press Return. The registry editor opens.
Before you edit the registry, you should make a backup. On the 'Registry' menu, click 'Export Registry File'. In the 'Export range' panel, click 'All', then save your registry as Backup.
Locate the HKEY_LOCAL_MACHINE entry:
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Systems Restart
"Rundll32.exe wnim.dll, DllRegisterServer"
and delete it if it exists.
Close the registry editor.