MiKTeX 2.9 (from the proTeXt DVD) fails to install on a fully patched Windows 8.1 Pro (x64) with the following error:
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MiKTeX Setup Wizard
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The operation could not be completed for the following reason:
Windows API error 2: The system cannot find the file specified.
Details: C:\Program Files\MiKTeX 2.9\tpm\packages\alg.tpm
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OK
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The path of the "failing file" varies with every attempt. For example I captured the setup attempt using LICEcap:

According to this question, however, no problems are to be expected (8.1 is essentially a service pack of Windows 8).
Does anyone know how to work around this and get it to install? I had no problems installing from the exact same setup (from the proTeXt DVD) on a fully patched Windows 7 (x64).
I tried both the DVD ProTeXt-3.1.5-031815.iso and ProTeXt-3.1.5-033015.iso. The hashes for these files matched the expected value.
ProTeXt-3.1.5-031815.iso(but the file was valid). I now downloadedProTeXt-3.1.5-033015.isoand while the file name of the setup issetup-2.9.4503-x64.exethe title bar shows the same as before. And the problem remains. Will try the basic installer now instead. – 0xC0000022L Jul 10 '15 at 14:25