Printer problem - won't scan

I have an HP printer, 4140 all in one. It will not scan. It will print from computer to printer without problem. It will not make a copy using the scanner bed. It keeps saying the device is not connected, yet it will print. I have uninstalled, reinstalled twice, one with software included with printer and with software downloaded from HP. This seems to be a common problem with printers, as I have had other HP printers that don't scan. Any suggestions of what to try before having to purchase a new one?

The system is Win Vista (32).

You can try it:
* Go into start->ControlPanel->SYSTEM->Hardware/DeviceManager, see here "Imaging Devices" or "Scanner", and do uninstall the scanner.
* Unplug your scanner
* And then click on Search [Start/Search] all files and folders, and [search "twain"] remove all references to twain [then search .ds and remove files. Not remove anything other than exactly ".ds" or files......
and after that ".ds." Windows may ask you to put in your Windows CD to copy new file...just click yes. [May be not ask.]

* Re-boot it
* Go into your SYSTEM, and remove USB Root Hub (if you have any USB devices, they will stop functioning..that's fine...they will work once you re-boot). If you have a USB mouse, push the "windows" button (on the left between CTRL and ALT, and use you tab key to highlight the
RESTART button.
* Once re-booted, the PC will find all your USB devices, and state all has been successfully installed.
* Plug in your scanner...windows will put in the software.
* Check it now............

Let me know if you got any problem..........

Thanks for all of that information. I did read that you can get the scanner to work through Paint. I tried that and it did scan. Still can't use the printer like a copy machine, but seems about 75% fixed.

So with the process that you outlined, I am going in and removing all kinds of files. Are these files that have accumulated over the course of time? This makes me wonder if this were a brand new computer, that the software from HP would work, but can't now because of these extra files. Or are these files corrupted? You would think HP would have a way to fix that. I just know this happens with lots of HP printers, losing the ability to scan.

I don't have the Windows CD, actually in another town due to process of moving for college. I will keep this information though, if I lose the ability to use Paint.