I've spent ages trying to overcome this issue, and it seems I'm not alone. Lots of people seek a solution for Error 1904 during an install of the Desktop Manager software.
Despite carefull uninstalling following Blackberry's rules here:
Error 1904 appears while installing the BlackBerry Desktop Software
the error would recur and when I connected my 8800 to my Dell latitude 531/Windows XP, I couldn't sync, in fact the whole desktop manager would grey-out as soon as the 8800 connected.
Uninstalls, reboots etc all failed until I tried removing registry entries as listed here:
How to peform a clean uninstall of BlackBerry Desktop Software - BBHub
Note that after each failed re-install I also routinely switch off and remove the battery from my Blackberry, and after following the regedit instructions in the above link, and then re-installing V4.3 software, I got no Error 1904, but needed to remove and then replace the 8800's battery to get it to work correctly.
Error 1904 - 'dll failed to register'
