A number of older ScanSnap scanners released by Fujitsu are no longer supported and the official line from Fujitsu is to buy new hardware. However, the ScanSnap range isn't cheap and you can avoid spending a large sum by utilizing Compatibility Mode built into Windows to get your older scanner working with the latest versions of Windows.
Update: 21st October 2017
A recent windows update caused issues with my 11-year old ScanSnap fi-5110ex02 - when the scanner was powered on, the ScanSnap Manager program could not detect the scanner and as a result I couldn't scan anything at all. "Oh well", I though, time to re-install the software using the guide below that I originally wrote back in 2012.
However, before proceeding - I noticed a comment from Chris Morse that said he managed to get his S510 working perfectly using the software for the ScanSnap iX500, which is fully supported on Windows 10. So I decided to give it a go for my fi-5110ex02 and I'm pleased to report that it worked perfectly.
It just goes to show that Fujitsu can support older ScanSnap devices on Windows 10, but simply choose not to do so in order to encourage people to buy new hardware.
1. Download Software
All drivers and software are available directly from the Software Downloads section of the Fujitsu website, organized by model number. Click through to your model (we'll be using the fi-5110exo2 in our examples) and you'll see a table similar to the one below:
Download the setup program for "ScanSnap Manager" and then select the Update tab to find the most recent software update made available by Fujitsu.
As you can see above, the last update made available for the fi-5110exo2 is for Windows 7. Download it anyway and make a note of the version of Windows as you'll need to know that when entering compatibility mode settings.
2. Disconnect or turn off your ScanSnap scanner.
You must ensure that your ScanSnap scanner is either disconnected or turned off until you reach step 7 - if you don't, then Windows will detect the scanner too early.
3. Uninstall existing ScanSnap software
If you obtained Windows 10 as an upgrade to Windows 7 or 8, then you will have the ScanSnap software already installed (but not working). It's important that you uninstall any existing ScanSnap Manager software and reboot before proceeding.
4. Install the Setup program
Firstly, ensure that the scanner is turned off and the lid closed.
Now run the ScanSnap Manager setup program that you downloaded in Step 1, which will extract the software to a subdirectory. Once extracted, navigate into the directory and run setup.exe to install ScanSnap Manager.
Reboot - If you don't, the next step probably won't work (it didn't for me with the fi-5510exo2)
6. Install the Update using compatibility mode
This is the final and the most important step. You need to tell Windows to run the ScanSnap Manager Update in compatibility mode for the version of Windows that it was created for.
Right click - do not double-click - on the Update program that you downloaded in Step 1, and Select "Troubleshoot Compatibility" from the context menu that appears.
Windows will launch the "Program Compatibility Troubleshooter", with options to use recommended settings or to manually choose compatibility settings. Select the second option, "Troubleshoot program"
We know that the update program was written for a prior version of Windows, therefore you should select the first option "The program worked in earlier versions of Windows but won't install or run now" and click "Next"
Select the version of Windows that the update file was designed for (which you noted down in step 1) and click "Next".
In the case of the fi-5110exo2 this was Windows 7.
Click "Test the program..." and the update program will run.
After finishing the installation, click "Yes, save these settings for this program".
7. Turn on your ScanSnap
Finally, turn on your ScanSnap scanner and it should be detected correctly. Perform a test scan to confirm everything is working as expected.
... and finally.
If you have tested a ScanSnap model which doesn't appear in the table at the top of this article then please post a comment below confirming the model number that you got working, the version of windows it is working on (e.g. Windows 10) and the version of Windows that was chosen in the Compatibility troubleshooter.