Windows 2003 SP2 and ISA Server do not always get along

1. Run ISA Server 2004 Enterprise Edition on Windows 2003 RTM/SP1? Make sure to install ADAM SP1 on the ISA Server Configuration Storage Server before installing Windows 2003 SP2.

2. If you run ISA Server on a multi-core / multi-processor 32-bit computer, and the CPU is heavily utilized, you might (will) experience performance degradation, due to a change in interrupt handling in Windows 2003 SP2. Install and configure the Interrupt Affinity Tool as a workaround. Read KB 934809 for more information.

3. Disable receive-side scaling (RSS) support in Windows 2003 SP2, by following the instructions here.

For more details on the issues, go here.