http://www.microsoft.com/whdc/archive/benchmark.mspx
"When benchmarking Windows XP, Microsoft strongly recommends a clean installation using NTFS. There are several reasons why performance for a clean installation will tend to be superior to that for upgraded systems. An upgraded system will constrain the placement of files and file system data. The old disk format may not use an optimal file system cluster size. In a clean installation, the placement of file system data on the disk and the internal organization of that data can be optimized, resulting in a smaller system footprint and fewer and faster I/Os when using the system."
"Benchmarking on a Dynamic and Self-Tuning Windows XP
Benchmarking an operating system that is attempting to improve itself over time based upon observed usage patterns can be difficult. It becomes ever more difficult to benchmark if the operating system is also attempting to create dynamic system restore points when large amounts of applications are installed. Fortunately, there is a methodology that provides consistent results, accurately reflects the performance that Windows XP systems will achieve, and is fairly easy to follow.
The basics of the methodology are:
•
Install
Install the OS and benchmark as normal.
•
Use
Run the benchmark one or more times.
OR
Use the applications in the benchmark as real users would.
•
Let Idle Tasks Run
Leave the system for a bit after using it, (up to three days for disk layout optimizations).
OR
Call the ProcessIdleTask API from advapi32.dll.
•
Test
Run the benchmark as usual."