It's well known that the Windows XP IDE device driver will gradually slow down over time. See this Microsoft article on the reasons. There are various web sites that provide information on resetting the driver to fix this problem. However, for systems with Intel chipsets a better solution may be to use the Intel Application Accelerator which replaces the Microsoft driver with Intel's own driver. Unfortunately, the current version (2.3) drops support of Mobile chipsets, and the previous version (2.2.2) which supports Mobile chipsets is too old to recognize the Centrino chipset. Fortunately, there's a way around this, which I describe here.
Since the 2.3 installer will not install its applications, we'll just use the 2.2.2 package. After you run this installer, it will copy its files to "C:\Program Files\Intel\Intel Application Accelerator" (or wherever your default program installation folder resides). But none of the drivers will be installed because the chipset is not recognized. The installer will tell you to restart the machine when it completes - don't bother until you've patched the drivers. We'll just refer to the Intel stuff as "IAA" for short.
In the IAA folder is another folder called Driver. Go in there and make a backup copy of the idechndr.inf file, so you can fallback if you mess up on these modifications:
c: cd "\Program Files\Intel\Intel Application Accelerator\Driver" mkdir bak copy idechndr.inf bak
Note, we're editing the driver inf to make it work with a chipset it didn't explicitly support. This may not be the safest thing in the world, so you're proceeding here at your own risk. Don't blame me if something blows up.
On the other hand, the Centrino IDE controller is an 82801DBM and the IAA does have support for the 82801DB already. And, the datasheets say that the two are functionally identical. So, assuming you don't mistype anything, this patch is perfectly safe. Still, the decision to go ahead is all your responsibility.
With that said, the modification is simple, just add 3 lines to the INF file: