Fix diagnostic.dll Errors

Windows files are commonly attacked by malicious software that prevents them from working properly. First step in addressing problems with diagnostic.dll file or any other Windows system files should be scanning the system for malicious software using an antivirus tool.

If by any chance you don't have any antivirus software installed on your system yet, you should do it immediately. Unprotected system is not only a source of file errors, but, more importantly, makes your system vulnerable to many dangers. If you don't know which antivirus tool to choose, consult this Wikipedia article – comparison of antivirus software.

Installing relevant Microsoft Windows patches and updates may solve your problems related to diagnostic.dll file. Use dedicated Windows tool to perform the update.

1. Go to the Windows "Start" menu
2. Type "Windows Update" in the search field
3. Choose the appropriate software program (name may vary depending on your system version)
4. Check if your system is up to date. If any unapplied updates are listed, install them immediately.
5. After the update has been done,restart your computer in order to complete the process.

Beside updating the system, it is recommended that you install latest device drivers, as drivers can influence proper working of diagnostic.dll or other system files. In order to do so, go to your computer or device producer's website where you will find information regarding latest driver updates.

System File Checker is a Microsoft Windows tool. As the name suggests, the tool is used for identyfing and addressing system file related errors, including those related to diagnostic.dll file. After an error related to%fileextension% file has been discovered, the program attempts to automatically replace the diagnostic.dll file with properly working version. To use the tool:

1. Go to the Windows "Start" menu
2. Type "cmd" in the search field
3. Locate "Command Prompt" result – don't run it yet:
4. Click the right mouse button and select "Run as Administrator" option
5. Type "sfc /scannow" in console prompt to start the program and follow the instructions

Another approach is to restore system to previous state, before the diagnostic.dll file error occured. In order to restore your system, follow the instructions below

1. Go to the Windows "Start" menu
2. Type "System Restore" in the search field
3. Start the system restore tool – it's name may differ depending on version of the system
4. The application will guide you through the process – read the messages carefully
5. After the process has finished, restart your computer.

If all the above-mentioned methods failed and the diagnostic.dll file problem has not been resolved, proceed to the next step. Remember that the following steps are intended only for advanced users.