There are two ways to manually delete index.dat files, safe mode or using the Windows task manager.

Windows Task Manager

1. Search for index.dat files
2. Make a note of the filepaths to the index.dat files
3. Start Windows Task Manager (Ctrl + Alt + Del)
4. Kill explorer.exe and iexplorer.exe
5. Go to menu " File
6. Click "Run..."
7. Type "cmd" + press enter
8. Navigate to index.dat files
9. Use "del" to delete them ( del index.dat + press enter)
10. Repeat the above steps (8-9) for each index.dat file
11. Restart explorer.exe in command prompt (cmd)
12. Exit command prompt and windows task manager

Safe mode

1. Restart your computer in safe mode
   How to: Hold down the key F8 during computer startup
   Select safe mode
2. Browse to your index.dat files
3. Delete index.dat files
4. Restart computer