First make sure you have the full featured software installed if it is available for your all-in-one. For the 2170, download the software from http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?prodNameId=90807&lang=en&cc=us&prodTypeId=18972&prodSeriesId=90805&taskId=135
. Uninstall a generic driver and unplug the USB cable before installing the full software (ie install software before plugging in the data cable). Avoid print servers and USB hubs; if there are any problems try a new cable first. Scanners require bi-directional communication so a bad cable will cause more problems with the scanner than with the printer.
Vista and Win7 both use a driver built into the OS; so just plug in the data cable. (If Windows Update is set to automatically install drivers for new hardware, it will quickly install the files. Otherwise check Windows Update.)
You can get the manuals from http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&lang=en&cc=us&docIndexId=64179&taskId=135&prodTypeId=18972&prodSeriesId=90805
If you have the full featured software, you will need to set up the destinations for the scanner buttons in the HP software. So start that program and scan from the computer first. (The buttons will not work if an HP monitor is not running to "see" the button presses.)
If you are using the OS driver, the buttons will not work. However, Win7 and Vista will acquire scans in several programs: Paint (File > Import from Camera or Scanner) and Windows Fax and Scan (New Scan) among others.
I hope this helps.