I found the following on Google.com

Name: JPW
Date: December 23, 2006 at 18:35:37 Pacific
Subject: H-P 5470c Can't find scanner.

Reply:
The Information below may help you solve the problem. I know that your Scanner is a different model, but the software and drivers install the same way.

HP Scan Jet 4200 & Windows XP SP2 Install Help
PROBLEM
When you try and install the Drivers for the Scanner you may receive the following error:
“HP Precision Scan LT
There is a problem with the registry settings.
One or more settings were reset to the default value. [2060].” or some other #.
Or when you go to use the Scanner you may receive the following error:
“Cannot find your Scanner
you may have a scanner connected to your PC,
but HP Precision Scan LT was unable to locate it.”
CAUSE for the PROBLEM
Both of the above error messages are the result of Windows XP SP2 Installing it’s own Drivers
for the HP Scan Jet.
SOLUTION to the PROBLEM
To confirm that this is the cause, Right Click on My Computer and click on the Properties
TAB, then click on the Hardware TAB, next click on the Device Manager TAB.
In Device Manager, go down and click on the Plus to the Left of Imaging Devices TAB.
It will expand to show the Hewlett-Packard Scan Jet 4200C (your model #) Double click on it.
The Hewlett-Packard Scan Jet 4200C Properties window will open.
Click on the Drivers TAB and look down to the line which tells Driver Provider.
If it has the word Microsoft for the Driver Provider then the information below will help you
resolve this problem. It should read for Driver Provider: Hewlett Packard.

If is has Microsoft as the Driver Provider then click on the Driver File Details TAB.
In the Driver File Details window you will find the Path for all the Drivers which Microsoft
installed for the Scanner. Write down the complete Path and file name for each file.
EXAMPLE C:\WINDOWS\system32\hpgt42.dll

Now go back to the Hewlett-Packard Scan Jet 4200C Properties window and click on the
Uninstall TAB. Once you have uninstalled the Microsoft drivers for the scanner, if it tells
you to restart your computer, just say NO! Close all the windows and then go into
C:\WINDOWS\system32 and either cut and past or delete all the files which Microsoft was
using to install the scanner. Don't hook up the scanner until the program ask you to hook it up.
DO NOT reboot until you have run the HP Scan Jet Software and drivers program.
Two things to take note of in this step: One is that I would cut & Past them to a different folder
until you have the scanner working under HP Precision Scan LT, then if you want to delete
them it is safe to do so. The second is that I have done this on two different Computers
and both of them were running Windows XP HOME SP2.
The 1st Computer was one I built my self for my wife, this one I was able to Cut & Past all files
while in normal Windows. The other one was a HP Pavilion and it would not let me Cut & Past
in Windows mode so I rebooted into Safe Mode and Cut & Pasted all the files.

Finally Reboot the computer and it will come up with a window to install the Hewlett-Packard
drivers, but will also complain about them not being Digital Signed, just click the continue
TAB, and when prompted to reboot do so and your scanner will now work just fine.