[G4] Quicktime MP4 problems!

[Thomas J. Fobia]

Hello all,

    I have a downloaded a drawing lesson that is a video MP4 file. I 
have a desktop Mac G4 where it doesnt play without jerks and sound 
dropouts. I burned the file to a CD and took to my laptop where it (the 
mp4 file) plays without any problems. The difference between the two 
computer are as follows: (Both using Quicktime 7.1.3)

My Desktop G4:
Mac OSX 10.4.8; 1.6 Ghz PowerPC G4 (Upgraded Powerlogix processor)
Memory: 1.12GB SDRAM

ATI Radeon 8500:

  Chipset Model:    ATY,R200
  Type:    Display
  Bus:    AGP
  Slot:    SLOT-A
  VRAM (Total):    64 MB
  Vendor:    ATI (0x1002)
  Device ID:    0x514c
  Revision ID:    0x0000
  ROM Revision:    113-85710-123
  Displays:
ULTRASCANP990:
  Resolution:    1024 x 768 @ 60 Hz
  Depth:    32-bit Color
  Core Image:    Not Supported
  Main Display:    Yes
  Mirror:    Off
  Online:    Yes
  Quartz Extreme:    Supported
Display:
  Status:    No display connected

and my laptop G4:
MAC OSX 10.4.8; 1.33 Ghz PowerPC G4
Memory: 768 MB DDR SDRAM

ATI Mobility Radeon 9550:

  Chipset Model:    ATY,M12
  Type:    Display
  Bus:    AGP
  VRAM (Total):    32 MB
  Vendor:    ATI (0x1002)
  Device ID:    0x4e56
  Revision ID:    0x0080
  ROM Revision:    113-xxxxx-117
  Displays:
Color LCD:
  Display Type:    LCD
  Resolution:    1024 x 768
  Depth:    32-bit Color
  Built-In:    Yes
  Core Image:    Supported
  Main Display:    Yes
  Mirror:    Off
  Online:    Yes
  Quartz Extreme:    Supported
Display:
  Status:    No display connected

Im thinking its got to be my video card in the desktop thats the problem 
(Since my desktop processor is faster then my laptop.

Anyone out there know of this type problem and can tell me how to get my 
desktop G4 to play this file without jerks and dropouts?

Thanks.
Tom