I TAKE NO RESPONSIBILITY OR WARRANTY FOR THESE INSTRUCTIONS WHICH ARE NOT AUTHORIZED BY HP IN ANY SHAPE OR FORM. IF YOU ARE FOLLOWING THESE INSTRUCTIONS, YOU ARE DOING SO ENTIRELY AT YOUR OWN RISK
I recently troubleshooted an HP LaserJet 1100A all-in-one device for someone. The problem is that the product has been discontinued for some time and HP has never made the scanner drivers available for Windows XP. After browsing through many forums online, I found a solution that actually works:
1. Install the original 1100A software for Windows 2000 which includes the scanning feature. If you do not have the original CD, you can order one from HP here. HOWEVER, it is also available for download freely right here. It is a 25 MB file so be prepared.
2. Download and install the hp LaserJet 1100A communications update from here. It is an 800kb file called "lj1100cuwinnt42kxp-en.exe". Install this update.
3. Download and install the HP Scanner Update utility for Windows 2000 for 1100A. This is what actually makes the scanner portion of the printer work with Windows XP.You can download it here. The file is called "lj188en.exe" and it is about 2.2 MB.
4. If you already installed the printer, go to its properties and change the driver to "HP Desktop". If you did not, install it now.
5. Make sure you have the HP Helper application in your system tray (to start it go to "C:\HPDESKhpdriv.exe"). Put something in your scanner slot and press the computer button on the printer. Your computer should popup a window asking if you want to copy or scan.
P.S. If you are looking for a replacement, there are several newer HP all in one Laser models you can find at Amazon.