I don't think it is only for mobile CPUs. If you read the link on MS hotfix, they state that:
- "Without these updates, computers that are equipped with these power management-capable, mobile, dual-core processors may experience decreased performance or unexpected behavior". I do agree that the grammar is a bit confusing. Does MS mean ONLY computers with ACPI + mobile + dual-core or computers with EITHER ACPI + mobile or ACPI + dual-core..... 

- "This hotfix also addresses the following issues on computers that have multiple processors that support processor performance states".
Vista is not affected. Windows XP needs to hotfix as it was not originally designed for multi-core CPUs that supports ACPI performance states..... Quote from MS:

"Windows XP SP2 is required on computers that have multiple CPUs that support ACPI processor performance states. This requirement includes computers that support the following items:
. Multiple physical sockets
. Multiple-core designs
. Multiple logical threads, such as Intel hyper-threading technology
Because Windows XP was not originally designed to support performance states on multiprocessor configurations, changes are required to correctly realize this support on multiprocessor systems. Windows XP Service Pack 2 includes the required changes to the kernel power manager. These changes make sure that Windows XP correctly functions on multiprocessor systems with processor performance states. "