As topic says Error writing file …\spotify\dsound.dll etc
Have reinstalled Spotify
Have checked permissions users have full control in spotify directory and files
Installer actually writes dsound.dll wirh 0 bytes size.
If you know what soundcard(s) you have, please include it! (ie. Asus Xonar, Auzentech or HT Omega)
Equalify Pro version
Any special software or hardware you might have installed:
ie. Razer Gamebooster or Cort
This is a common error with windows installer and is usually a permission issue of some kind. For Equalify pro its usually either the spotify folder ( %appdata%/Spotify ), the dsound.dll file (in the spotify folder) or your temp folder ( %temp% ) that does not have the right permissions, make sure you and the system user has read/write access to them all. If there is a dsound.dll file in the spotify folder, remove it before installing.
You can also try moving the installer to another folder - copy it to your desktop and see if it will run correctly from there.
What happens if you try to install to a completely different directory ?
Did you also move the installer to your desktop ? (the installer being in the wrong folder can actually cause issues like this, its a known problem with windows installer)
And did you delete the dsound.dll in the spotify folder if its already there before installing ?