Sorry to hear you are so frustrated with the installation. I would like to verify first that in the title you have put Officejet 8000 which is a single-function printer. The A909g is the Officejet 8500 Wireless which is what I assume you are trying to install.
First, allow me to explain why it is not installing correctly. If a user repeatedly uninstalls/re-installs for whatever reason, it leaves left over files in the registry and causes errors in the device manager such as this. I will try an easier step first to get this problem resolved but it can get quite complicated if you are experiencing errors such as this. I will do my best to keep this as painless as possible.
You need to clean out of every instance of this printer from your computer. I could walk you through how to do this manually but I think you would benefit from doing what is called an L3 uninstall. To do that, you have to click here to begin the download process of the Officejet 8500. Once the extraction process is complete, cancel the installation.
Next, click the Windows button and type in the search field %temp% and search in here for a 7z folder that contains the information about your printer (example: 7zS2356).
Once you find it, open the Util folder, then open the CCC folder and run the uninstall_L3.
This should remove every instance of the printer from your computer. After the uninstall requires you to reboot the computer, to make sure it removed everything, check your program files and x86 program files. If you see any leftover Hewlett Packard/HP folders that contain information on your printer, then delete them as well.
Next, go to All Programs>>Accessories>>System Tools>>Disk Cleanup. Run the Disk Cleanup tool to get any other files that might still be in there. You have to cleanup the computer or the printer may never install correctly again.
Reboot the PC by turning it off completely and turning it back on. Now try to install the printer's software again. I recommend using the HP Printer Install Wizard. The link above I have provided is for the US version from the website. The Install Wizard will find the best suitable driver for your printer.
This is the easiest way to do this. If this does not help, then I will have to modify these steps based on the brand name of the computer you have. So answer these for me please if the steps above do not help or if you have any more questions I will need to know:
1. What is the brand name of the computer you use (HP, Dell, etc)?
2. How is the printer connected (USB, wireless, or Ethernet)?
3. Do you have the Officejet 8500 Wireless or the Officejet 8000?
4. What anti-virus software do you use? Some AVs can cause errors like this as well.
I am happy to help!