There is no "install" or "setup" file needed. Save the zipped file, uniden_usbser.zip to your PC.
Then, use Windows Explorer, WinZip, 7Zip, or another compressed file to extract the file folder.
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Inside the folder are two files.
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The file with the *.inf extension is the driver.You can leave it wherever it is after you extract it, or copy it down into the driver folder in Windows (that's not really necessary, but you can do that)
Now that the extracted file uniden_usbser.inf file is on your PC, go to the Device Manager. On older versions of Windows, that was a separate control panel icon. Later Windows versions (like the Windows 7 machine I am using at the moment) have the Device Manager under the System icon.
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Click on Device Manager to open it.
Find the Ports listings and click to expand it.
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You indicate you see an error on the port, right?
<Right><Click> on the port that indicates an error (usually a yellow exclamation mark).
You'll get a pop-up menu like this:
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Select the "Update..." option.
At the next screen, you can tell Windows to check for the correct driver, & it should find it, as long as you have the extracted (not zipped) files saved on your PC.
Or, use the 'Browse My Computer......' option and then browse to wherever you saved the file, then click on the *.inf file.
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That same driver is used for both HP models, as well as the 325P2 & 996P2, the 436HP/536HP, and SDS100/SDS200 scanners.
While my screenshot shows it on Com 6, your PC may use a different one. Also, you may see the Com Port number different if you later use a different USB port, instead of the one used initially.
Once you get the driver installed correctly, then, in ProScan , use the CommPort link at the top of the ProScan window, and let Auto Detect find it, then you can set that selection in ProScan.