By coincidence, when I bought a replacement all-in-one HP for my wife over the weekend, I had the same problem, and this was becuase, altrhough I removed the old printer software, I didn't bother to remove the old scanner software, so it failed to reinstall the correct versions.
Even if this is not exactly your problem, when you installed the printer, you may not have installed the scanner software. When you do install the scanner software, an icon should appear on your desktop providing the access to all the tools you need.
IMHO, the best approach is to uninstall all the printer software, making sure that the folder (I think its something like C:\Program file\HP\) is deleted, and then run a comkplete re-install. Be4 alert to the fact that you may have a wait after the prionter has installed before the other software installs, and you may have to slect to install it separately. Unfortunately, the manuals are not particualrly specific so make sure you install everything from the DVD.