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:
Getting an error: C:\Users\"user"\AppData\Local\Temp\mdi564.dll The specified module could not be found "?
The likely reason for these files being missing, is that your Anti Virus software has removed them due to suspicion of PUP or danger. To stop errors for this file, remove any leftover start up entries.
How to remove the Startup entry:
Win XP, VISTA, 7: Press "Windows"-key + "R" to bring up the "Run" dialogue. In "Run" dialogue type "msconfig" and hit Enter Under the tab "Startup", uncheck any boxes relating to these files. Win 8: Press CTRL+SHIFT+ESC at the same time to bring up the Task Manager. Under the tab "Start-up", uncheck any boxes relating to these files.
Should you not find any mention of the missing file here, try instead Microsoft Sysinternals Autoruns, available for free at http://technet.microsoft.com/en-US/sysinternals/bb963902.aspx