Drivers installed right, but no digtial audio {sony pcv 7762} could it be the motherboard.

Could it be the motherboard?
Yes.

Could it be that it is the wrong drivers?
Or the right drivers, and installation did not actually occur?
Yes.

If it is the motherboard's integrated audio chipset is bad, simply obtain, and use a sound card in the appropriate expansion slot on the motherboard.
An open PCI slot. (White in color)

[NOTE* That is PCI-Express x1.
Not PCI-Express x16 slot. This slot is reserved for a graphics card.

According to Sony eSupport the PCV 7762 model is actually the PCV-RX850

1) Did you install this audio driver?

http://esupport.sony.com/US/perl/swu-list.pl?mdl=PCVRX850

Yamaha YMF753 Audio Driver Utility?
(Has the audio driver in it)

2) You downloaded the file to your computer (My Documents, or Downloads, perhaps?), and then double-clicked on the file name - YA31520801JG.EXE, then followed the simple instructions of the Installation Wizard?

[Simply, Next, Next, and Finish]

3) You then restarted the computer?

4) Are you sure the audio is turned on, and not muted? (Speaker icon in system tray, or go to Control Panel)

5) Sound system is plugged in correctly to the back of the computer? (Motherboard)

6) Sound system has power to it if required?

7) Still using the Windows XP O/S that came with the computer?

One example of a PCI soundcard,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4459743&CatId=2771

For additional questions please post in a Comment.
Regards,
joecoolvette