Question : Problem: No HP devices have been detected.  HP Solution Center will close now. L7650 working otherwise

Windows XP
HP Officejet L7650 All-In-One
Computer had been using this printer with USB.  Change to ethernet / network configuration.
Software no longer recognizes printer - reinstalled HP Basic download.  HP Solution Center no longer works. Printer works.
Workaround for scanning is to execute hpqscnvw.exe but capability to print to .pdf file is missing.

Uninstalled all HP software.
Downloaded and installed "FULL" software.
Computer appears to think that there is already a device installed....
Install the printer but the HP install doesn't see the network printer. (???)  Is this a clue?
Manually setting the port for the printer does allow the printer to work.
Intall HP Imaging Device Function 8.0
Get HP Solution Center but it stops with "No HP devices have been detected.  HP Solution Center will close now."
Still using the workaround.
Want to get HP Solution Center working so that .pdf file printing from scanner will work.

Answer : Problem: No HP devices have been detected.  HP Solution Center will close now. L7650 working otherwise

The owner lost interest and is using a workaround.  I'm most disappointed with HP on this one.  I've also seen the problem at another site.  It seems to be associated with having one AIO installed and then adding a second, newer one.