I keep getting this warning. I use a 1TB Seagate external hard drive.
Problem ejecting drive.PNG

It occasionally ejects just fine, but mostly it keeps giving me this warning, even after I've long closed out all other programs.
I use a custom built computer with an EVGA GTX 960 graphics card, an Intel Quad-Core i7 CPU, with a Samsung EVO SSD.
Download WinObj and Procexp from sysinternals WinObj and Process Explorer
  • Open Winobj with "Run As Administrator" and expand Device and locate your USB drive. If you only have one internal drive it will be Harddisk1.
  • Right click on it and select Properties.
  • Under the Details tab, References if Handles is greater than 0 then a process has something on the device open
  • Now Open procexp with "Run As Administrator"
  • Click on Find at the top and type in the disk name and click search for this example Harddisk1
  • Select the process and it will highlight the process and the handle in question
  • In the lower pane of procexp you can right click the handle and close it (please note this could corrupt data on the drive)
  • Once the handle is closed you can safely eject the drive.