Copy both .dll files from your \i386 Folder of your XP disk in dos mode, to your main windows directory.

Simply start from dos, choose your cd rom directory..eg D:/
open the /i386 folder....D:/cd i386
type : copy SHLWAPI.dl_ c:\windows\system32 = This would take the SHLWAPI.dll usually found at root and copy it into the windows directory.
now the SHLWAPI.dll file is also located in the Lastgood\system32 folder and the Lastgood\system32\dllcache thou you should only need to copy it the system32 folder to allow you to access windows from boot.

Do the same with the msgina.dll as it is found in the same directories.

hope this helps, I would only do this if you cannot do a repair from xp disk first