I downloaded the 4.5 file manager, then i installed it. After installation, (at the Finish window) the threatfire program in our PC alerted me to kill and quarantine the process, which is the program (DriveHQ) connecting to the internet. I said yes and it quarantined some files of the program.

When I tried to run the program through the desktop shortcut, it just tries to reinstall itself. But during installation, a window will pop out that says:

"The following error occured on the file 'C:\Program Files\DriveHQ File\DriveHQ FileManager\ShellCopyHookDLL.dll'.

Access is denied.

(0x5)"

My question is how to fix this error so that I can reinstall the program?

The problem as you described is caused by your firewall / anti-virus software incorrectly blocked DriveHQ FileManager. ShellCopyDll is a file used to support drag and drop between DriveHQ FileManager and Windows Explorer (My Computer). Please make sure you don't block DriveHQ software installer and DriveHQ client program.

In your case, you might have to disable your anti-virus / security software and then reinstall DriveHQ FileManager.