Would appreciate help: laptop/xmod/stuttering issues

Since i am going to be my own DJ at my wedding in a little over a month (penny pinching), i bought a second hand laptop and a few other bits and pieces to hook up to the hired amp / speaker system, and have got my playlist. I got the Xmod for better sound quality, and it really works well on my desktop, it really is better quality.
All is going well, but got an issue that's p*&%ing me off, and would seriously do with any feedback or ideas please as i'm all out.

System
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Compaq n410c laptop (P3 1.2 Ghz, speedstep turned off, 768 MB RAM, fresh install of WinXP Pro SP2, all updated).
Sitting in the dock / extender (but problem exists in or out of it)
iTunes 7.2
All updated drivers
Creative X-mod (external soundcard-type device)
Music is stored on the laptops internal hard drive.

The issue
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When i select music, it begins to skip within a few seconds (eg Britney Spears sings "Oh b..baby...ba.....by" which some might say is an improvement, but still) and doesnt resolve itself.

What i have tried so far
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- Updating drivers for sound card - this is the onboard, but a waste of time as it is bypassed anyway, and have even disabled the onboard.
- Converting MP3 to AAC, then playing AAC
- Changing speedstep to on, and also off.
- Monitoring CPU usage to see if that's maxed out. Typically hovers around 15 to 35%, no more.
- Trying different USB ports, both on the laptop and also the dock extender. They are noted as being USB 2.0, have checked also in device manager.
- Playing the Xmod via my desktop machine (iTunes on an Athlon X2, see my system spec), and all works smoothly and well.
- Have also rebooted after plugging in the Xmod.

When i hook the laptop (using its internal sound device), the music plays smoothly, only at lower quality.

So
==

It doesn't appear to be a CPU issue, and sound format (mp3) issue, a hard drive issue or a USB issue.
I know the machine surpasses that Xmods minimum requirements. I know the Xmod works on its own, and the laptop works on its own. Just not together.
Really appreciate any suggestions, thanks guys & gals.

Have also tried a spare, crappier Toshiba tecra 8000 laptop (a P2 366, old, heavy and slow) which works perfectly.
Now i'm upset.

Have tried installing Intel Application Accelerator and any other chipset related stuff to the i830mp motherboard, no joy so far.
:(

Edit: Could it maybe be a USB issue after all, since the xmod is USB powered? Is it possible that my laptop usb sockets are not good enough to provide power and clean / fast data?

Additional: Have now tried using Winamp instead of iTunes. No joy, exactly the same issue. :(

Success!
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(sort of)

I will leave this thread here for any future people in a similar state.

I have just plugged my n410c laptop usb port into my dell monitor, which also acts as a powered usb extender.
Laptop -> powered usb hub -> xmod and all is well! No stuttering, crackling or anything!

So i now need to get a powered USB hub in order to use the laptop at the wedding, but at least the cause is identified.

Hope this helps some other poor sucker..er..soul