Hp Compaq Dc7800 Drivers

i tried to help somebody with his compaq dc7800 minitower convertible which had been affected by viruses.i clened the viruses from partition d and repaired the partition c: using windows xp sp2 ver 2002 after which the computer started restarting itself when it reached the windows logo.i repaired it again and this time round it booted but the sound was gone.i have tied so many rdrivers but to no avail.the error they give is either "driver not found /hid missing"this is when i use soundmax drivers and drivers i found on hp website called adi.secondly the computer cannot detect flash drives.usb modems/anything.it says it has found new hardware which when you try to install says the drivers could not install.in device manager the intel(r)magement engine & modem have exclamation marks.on the other partition which i formatted with the same xp sp2 ver 2002 can detect the flash drives and even the modem but when you try to intall sound it says something like hid driver not found.please help i cannot format partition c: if i do not know what drivers i must intall to get a full functional machine.it also has very important documents in drive c: and i have no back up utility.please help me know which drivers are needed and where to get them on the internet.im really frustrated.please help me.