Received the follow messages:
1) You can get full scanning features by
installing the software for the 5100C scanner.
Be sure to have HP PrecisionScan 1.02. If you don't you can download it
here:
ftp://ftp.hp.com/pub/scanners/software/sj263en.exe 
Download the patch for Windows 2000 here: 
ftp://ftp.hp.com/pub/scanners/software/sj269en.exe 
Download the patch for the copy utility if you own an USB printer here: 
ftp://ftp.hp.com/pub/scanners/software/sj536en.exe  
Download the newest
EPST driver here:
ftp://ftp.scmmicro.com/connectivity/drivers/epstw2k.exe 
Instructions:
1. Boot the computer with the scanner turned off or disconnected.
2. Install HP PrecisionScan 1.02 and DON'T reboot yet.
3. Run the Windows 2000 patch (sj269en.exe)
4. Reboot with the scanner connected and turned on.
5. Windows will complain about hpppt.exe not starting, so go to
Start-Programs-Startup and delete the shortcut to "HP Parallel port
test"
6. Open the registry (start menu - run, type "redegit"), go to
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunOnce and
delete the item with "hpppt" in it.
7. Open the device manager (control panel - system - hardware tab - device
manager button), open the "Ports (COM & LPT)" section,
double-click on the LPT port your scanner is connected to, click on the
"Port settings" tab and select "Use any interrupt assigned
to the port".
8. Reboot.
9. Extract epstw2k.exe in a folder
10. Open the device manager and open the "SCM PPort SCSI adapter",
which is found under "System devices" and update its driver
pointing to the folder with the new drivers in it.
11 (Optional) install the patch for the copy utility if you own an USB
printer. (sj536en.exe)
12. (Optional) If the hardware icon in the task bar annoys you, double
click on it and deselect the "show icon in task bar" option. 
Happy scanning!
Thanks to Sebastian for the instructions
2) The fix listed on your site for the HP Scanjet 5100C for W2000 dated 5/00 does not work for me. My W2K Pro reports that the system cannot load the drivers (from epstw2k.exe) for the SCM PPort SCSI adapter.

Install the drivers as per Windows 2000 (Win98 Drivers plus the patch) and run the Scan Wizard from within Whistler (acessible from the Control Panel or My Computer) HP's Precision Scan does not work, however the new scanning wizard in Whistler seems a lot better than Precision Scan. The Whistler version used is 2416, I have not tested it on other releases.
http://www.hp.com/cposupport/swindexes/c5197a_swen.html

Simply let Whistler detect the scanner during installation. It works perfectly, albeit using the scanning wizard built into Whistler. Scans perfectly straight into Office 2000 applications too. I didn't test it yet with Photoshop or any other graphics applications. There is no need to install any HP software at all.