Jun 1, 2014 - Hi: For the serial port driver you need to install the amt driver from the link below. The W7 driver should work. You may have to manually install. Download the latest drivers for your HP Compaq dc7900 to keep your Computer up-to-date. ICH10 Family PCI Express Root Port 1 - 3A70. PCI Serial Port: Driver.

The basic board spec shows it does not have a Serial port. However it does have an Intel Management Engine interface for which the drivers should be. If you read the driver page it informs that if these drivers are not installed it shows as missing drivers for a Simple Communications controller.

To be clear serial ports are legacy devices and seldom used today. If not actually needed the lack of drivers for this specific device would have no effect on the system The specification also says nothing about a parallel port (Lpt1). Do you have an expansion card into which you plugging in the printer. The socket would not be in the main group of connectors but separate and in the vertical slots.

Some port expansion cards had both Serial and parallel ports so this might be the missing driver. If so you would need to identify what the card is and find the appropriate drivers. Unfortunately it is highly likely they would not be available for Windows 7.

The spec of the Printer does not show USB so have you got a USB to Parallel converter, In which case that is going to need drivers itself. Venerable and functional it may be but the 710c is a very old printer and although it may work if set up right is not supported on Windows 7.