As from this link , the drivers for most HP printers are already built-in to Snow Leopard. Thus, they didn't recommend reinstalling driver from your HP printer CD.
Here are some excerpts regarding scanning feature on Snow Leopard from the link:
The Scanning interface is now built into Snow Leopard and supported with the Apple Image Capture application. Instructions follow.
HP Scan Pro software (from Mac OS X 10.4, 10.5) is not supported in Snow Leopard. The HP icon for HP Device Manager still in the dock after upgrade is not functional and should be removed.
Scan support from pushing the Scan button on the printer is not supported with this version of the scan interface built into Snow Leopard. Scan functionality is supported by scanning directly from the computer.
** there are methods on how you can scan on Snow Leopard from the link that I've given above. But I'll paste here Method 3:
Method three: Scan from Print & Fax > Printer browser
From the Apple menu, choose System Preferences .
Click Print & Fax .
In the list of printers on the left side of the dialog, select the HP All-in-One to view the options in the Print & Fax window.
Click the Scan tab, and then click Open Scanner .
The Printer Browser window appears.
Click the Scan icon at top right of the toolbar to launch scanning.
The scan interface opens. Click Show Details to view settings and options.
If the Scan
icons do not appear in the Printer Browser
window toolbar, you need to delete the current HP printer queue and add a new one, as follows:
Close the Printer Browser window to return to the Print & Fax preference pane. Or, go directly to the System Preferences > Print & Fax pane.
Select your HP printer in the list on the left.
Click the - sign at the bottom of the list to delete the product from the list.
Click the + sign at the bottom of the list to add the product back to the list.
Select your HP printer, and then click Add to create a new print queue.
The next time you open thePrinter Browser window, the Print and Scan icons should appear in the toolbar, providing access to Image Capture.