SYMPTOMS

A program that uses large mapped file views to share information between two processes may experience a significant performance decrease. The performance degradation occurs in the UnmapViewOfFile function. CAUSE

This problem occurs if you install Windows XP Service Pack 1 (SP1) on an Intel Pentium 4 computer that has more than one logical processor.

RESOLUTION

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows XP service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

Download the fix Q815227 Hyper-Threading Update - Techconnect

Thanks Neowin for the update!