I found that when installing Lion from a formatted drive, the ppd files for HP printers aren’t present. You can get them from the previous OS install disc (snow leopard), in the following location (it’s hidden, so use CMD-K in the finder to browse to it):
/Volumes/Mac OS X Install DVD/System/Installation/Packages/
In there you should find a set of all the printer drivers for various printers that could have been installed previously. I recommend using grep to determine which package has the driver you are looking for.