Hello.

My computer refused to run Half-Life Episode Two on the account that it
hadn’t DirectX 9.0c installed. OS is WinXP Eng SP2 (incl. all updates) and
when I started dxdiag it showed 9.0c was actually installed. I downloaded
newer (then August 9.0c) version and deinstalled current DirectX using
DirectX Remover. Then restarted PC but when I tried to install new 9.0c it
didn’t let me do it. The log says "GetDXVersion() Failed".
I tried to find registry keys and I found this
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectX - "Version". What value I
should set in order to make it installed. I know I did the action one
shouldn’t do, but this is strange that DirectX just can’t recover itself by
new install. Video-card is nVidia GeForce4 MX 440. If it doesn’t support 9.0c
so how can I install earlier version of DirectX? Again what values should I
set in registry? Please, I call for your suggestions (hope I don’t have to
reinstall OS).

I found solution to my problem. System will still suffer minor issues after
you apply this but at least you won’t have to reinstall OS from scratch.
First of all make sure you accidently deleted DirectX and there is no other
way to recover it.
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You’ll need:
[a] original WinXP distributive WITHOUT ANY service packs embedded
[b] latest DirectX
[c] DirectX Happy Uninstall (this software uses broken English but it knows
its stuff).
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[1] Extract WinXP’s I386 folder to any path, say, C:\RecoverDX\I386
[2] Extract contents of latest DX package into, say, C:\RecoverDX\DirectX

You MUST NOT run anything from these ^ folders, they will be used/run by
DirectX Happy Uninstall.

[3] Uninstall residue of DX by applying DirectX Eradicator 2.0 and DirectX
Remove (DxRemove.inf) software and restart PC
[4] Run DirectX Happy Uninstall, recover DirectX 8.1 pointing to
C:\RecoverDX\I386 folder and restart PC
[5] Run DirectX Happy Uninstall, install latest DirectX pointing to
C:\RecoverDX\DirectX and restart PC

If you did everything as described above, dxdiag.exe will indicate that DX
is running properly.
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I hope Microsoft will introduce own DirectX recover function into following
releases.