Windows XP Service Pack 1 brought about many fixes for Microsoft's flagship operating system, but a change to the memory management system caused applications on some machines to run much slower.
A source told BetaNews that most performance complaints received by Microsoft came from users running a Pentium 4 processor. Microsoft recently acknowledged the problem and privately issued a hotfix, but a patch has not yet publicly appeared on Windows Update or Microsoft's Download Center.
Service Pack 1 was released last September after months of beta testing. The upgrade includes many enhancements to Windows XP such as USB 2.0 and the .NET framework.
The memory manager in Windows XP was updated to increase security, according to Microsoft, but the fix negatively impacted programs that frequently allocate and deallocate memory. Such programs could take up to ten times longer to execute.
News source: BetaNews