Correct, you should not rename the extpack file, because that can mess up things with the identification. The error is not very helpful, but it might mean that the file is not downloaded properly. Check the file checksum with the following:
- Code: Select all Expand viewCollapse view
[MD5] 9ca47480f5b6339a607320c02529c02c Oracle_VM_VirtualBox_Extension_Pack-4.0.0-69151.vbox-extpack
[SHA256] ee17dff369901d3d5232aad4f4a3712d6a40074d02fb45f575657bf2d5946f3c Oracle_VM_VirtualBox_Extension_Pack-4.0.0-69151.vbox-extpack
Get the checksums using a checksum calculator for files and compare it with the above. Try a different browser too, that can also cause problems. And security software, that has a tendency to corrupt files as well during download.