MSConfig.exe is located in C:\Windows\PCHealth\HelpCtr\Binaries\MSConfig.exe.
Go to C:\Windows\PCHealth\HelpCtr\Binaries\ and check if MSConfig.exe file is there or not. If it’s not there, you can copy it from another computer to the Binaries folder or if you only have Windows XP CD, open a command prompt window, insert your XP CD into the drive and enter the following command: (assuming D is your CD drive and C is where your Windows is installed)
If you locate this entry in the registry HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\MSCONFIG.EXE, in the right pane, next to Default, it should show: C:\WINDOWS\PCHealth\HelpCtr\Binaries\MSConfig.exe
You have those 2 entries, correct?
If Msconfig.exe isn't under the App Paths key try this. Open Regedit.exe and navigate to: