The .exe extension on a filename indicates an executable file. Executable files may, in some cases, harm your computer. Therefore, please read below to decide for yourself whether the mididef.exe on your computer is a Trojan that you should remove, or whether it is a file belonging to the Windows operating system or to a trusted application.
Description: Mididef.exe is not essential for the Windows OS and causes relatively few problems. The mididef.exe file is located in the C:\Windows folder.
Known file sizes on Windows 10/8/7/XP are 49,152 bytes (57% of all occurrences), 24,576 bytes, 25,600 bytes, 20,992 bytes or 25,088 bytes.
The program has a visible window. The application starts upon Windows startup (see Registry key: DEFAULT\Runonce, Run, DEFAULT\Run). The file is not a Windows core file. Therefore the technical security rating is 23% dangerous; but you should also compare this rating with the user reviews.
Recommended: Identify mididef.exe related errors
If mididef.exe is located in the C:\Windows\System32 folder, the security rating is 14% dangerous. The file size is 28,672 bytes (66% of all occurrences) or 25,600 bytes. The program has a visible window. The program starts upon Windows startup (see Registry key: DEFAULT\Runonce, Run, DEFAULT\Run). Mididef.exe is not a Windows system file. mididef.exe appears to be a compressed file.
External information from Paul Collins:
Important: Some malware disguises itself as mididef.exe, particularly when not located in the C:\Windows folder. Therefore, you should check the mididef.exe process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.
A clean and tidy computer is the key requirement for avoiding problems with mididef. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic Update. Always remember to perform periodic backups, or at least to set restore points.
Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the 6resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.
To help you analyze the mididef.exe process on your computer, the following programs have proven to be helpful: ASecurity Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. BMalwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.