This is not a newer DirectX than 8.1a (Home user) It's simply an updates redist file for developers to include with programs that require DirectX. Since its across all Os'es it doesnt hurt to have it backed up tho..
I just installed it on both 2000, and 98. It changed my DirectX version from 4.08.01.0881 to 4.08.01.0901. Some of my DirectX files have May 2002 file dates. I haven't done any tests other than the DXDiag stuff.