Just exploring here now...
- Laptop
- Inconsistant server play in dedicated mode
- XP Used to work in a previous Service Pack
You didn't comment about other things running on the laptop in the background. I realize you said the TaskMgr was of no help, but that can be deceiving.
So, try removing or stopping all unnecessary programs and services just to be sure they don't matter. Include in this any resources being shared from the laptop like printers. The game and only the game.
Still no difference... try another thing while you've slimmed things down... try running the server in Non-Dedicated Mode. I have seen laptops [especially Sonys] that would not give fair cpu attention to a task unless it was doing video IO. If this makes things better... we need to look to laptop BIOS settings and drivers [no matter how it
USED to work]
I'll stop here and wait for some answers. [BTW - I forgot to ask what game revision you're running]