Microsoft has released a knowledge base article that describes that the company has updated the Windows XP kernel to accomodate a fix for Intel Pentium 4 HyperThreading capable CPU's. According to the article, 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. 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. The kernel files are updated to version 5.1.2600.1202 once installed. Unfortunately the update is not yet publicly available. Should you obtain information on how to get it, please leave a comment.