Quirky DVD volume levels...

Had Motophoto convert DV tape to DVD.
DVD video & audio were fine on Dell desktop, Dell laptop and DVD player.
Had them convert VHS, VHS-C and 8mm film to DVD's.
Video fine on desktop, laptop & player.
When playing DVD's on desktop audio is present but have to increase volume
25 clicks above normal to hear and then there is a slight buzz in the background.
Audio on same DVD's plays fine on laptop & player.
Motophoto used a Sony burner for all conversions and cannot understand why DV on desktop is ok but on the VHS & VHS-C’s the volume is unacceptable. They played the DVD's on their equipment and the volume was at an acceptable level. They feel they have met their obligations in that the DVD's play on the laptop & player. I have asked them to provide me with the model number of the Sony burner.
It is critical that the DVD's work on the desktop in that it is has more memory, larger screen and keyboard. My goal in these conversions is to edit and produce my own DVD's. I have successfully completed this on the initial DV to DVD conversion.
Made a copy of one of the fully functional DVD's on the laptop. The audio on the copy played fine on the laptop. When I tried it on the desktop the audio issue again reappears.
Have tried commercial DVD's & CD's on the desktop and the volume is fine.
Have not added or deleted hardware or software since long before starting this project.
Will provide any additonal info needed.
Would appreciate any thoughts on overcoming this limitation.

Desktop specs: (unit is 16 months old)
Operating System Microsoft Windows XP Home Edition
OS Service Pack Service Pack 2
Motherboard:
CPU Type Intel Pentium 4E, 3400 MHz (4.25 x 800)
Motherboard Name Dell Inc. Dimension 8400
Motherboard Chipset Unknown
System Memory 1024 MB
BIOS Type Phoenix (10/11/04)
Display:
Video Adapter RADEON X300 Series Secondary (128 MB)
Video Adapter RADEON X300 Series (128 MB)
Monitor Plug and Play Monitor [NoDB] (C06464BA302L)
Multimedia:
Audio Adapter Intel 82801FB ICH6 - AC'97 Audio Controller
Audio Adapter Sound Blaster Live! 24-bit [NoDB]
Device
Disk Drive ST3160023AS (160 GB, 7200 RPM, Serial-ATA/150)
Optical Dirves: HL-DT-ST DVD-ROM DGR8163B & Philips DVD+-RW DVD8631