Please I'm also having the same problem. I just reinstalled windows 7 on my HP DC7700 and the only drivers missing are PCI SERIAL PORT and PCI SIMPLE COMMUNICATIONS CONTROLLER.
I have checked the HP drivers download page but could not find anything. The only drivers I saw were for windows Xp and vista which I tried downloading and installing but got error message that it does not support the operating system.
Kindly help me because as it is now, I cannot instal any printer on my system. I have HP printers (Laserjet 1200, 1320 and CP1515) that I needed to instal on the system.
Thank you.