Source and binaries (amd64 and x86) attached.

Pseudocode:

list acm_drivers;
acmDriverEnum( myCallbackFunction, &acm_drivers, ...);
    // myCallbackFunction(driver, pacm_drivers) { pacm_drivers->add(driver); }
for each driver in (acm_drivers) {
    details = acmDriverDetails(driver);
    print details;
}

Output on my system - spot the bug!

>acmenum.exe
ACM Drivers found: 6
-- ACM Driver Details: Microsoft IMA ADPCM --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 1
    wPid: 34
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x04000000 (4.0.0)
    fdwSupport: 0x00000001
        ACMDRIVERDETAILS_SUPPORTF_CODEC
    cFormatTags: 2
    cFilterTags: 0
    hicon: 0x0000000000000000
    szShortName: "Microsoft IMA ADPCM"
    szLongName: "Microsoft IMA ADPCM CODEC"
    szCopyright: "Copyright (C) 1992-1996 Microsoft Corporation"
    szLicensing: ""
    szFeatures: "Compresses and decompresses IMA ADPCM audio data."

-- ACM Driver Details: Microsoft CCITT G.711 --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 1
    wPid: 37
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x04000000 (4.0.0)
    fdwSupport: 0x00000001
        ACMDRIVERDETAILS_SUPPORTF_CODEC
    cFormatTags: 3
    cFilterTags: 0
    hicon: 0x0000000000000000
    szShortName: "Microsoft CCITT G.711"
    szLongName: "Microsoft CCITT G.711 A-Law and u-Law CODEC"
    szCopyright: "Copyright (c) 1993-1996 Microsoft Corporation"
    szLicensing: ""
    szFeatures: "Compresses and decompresses CCITT G.711 A-Law and u-Law audio data."

-- ACM Driver Details: Microsoft GSM 6.10 --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 1
    wPid: 36
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x04000000 (4.0.0)
    fdwSupport: 0x00000001
        ACMDRIVERDETAILS_SUPPORTF_CODEC
    cFormatTags: 2
    cFilterTags: 0
    hicon: 0x0000000000000000
    szShortName: "Microsoft GSM 6.10"
    szLongName: "Microsoft GSM 6.10 Audio CODEC"
    szCopyright: "Copyright (C) 1993-1996 Microsoft Corporation"
    szLicensing: ""
    szFeatures: "Compresses and decompresses audio data conforming to the ETSI-GSM (European Telecommunications Standards Institute-Groupe Special Mobile) recommendation 6.10."

-- ACM Driver Details: MS-ADPCM --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 1
    wPid: 33
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x04000000 (4.0.0)
    fdwSupport: 0x00000001
        ACMDRIVERDETAILS_SUPPORTF_CODEC
    cFormatTags: 2
    cFilterTags: 0
    hicon: 0x0000000000000000
    szShortName: "MS-ADPCM"
    szLongName: "Microsoft ADPCM CODEC"
    szCopyright: "Copyright (C) 1992-1996 Microsoft Corporation"
    szLicensing: ""
    szFeatures: "Compresses and decompresses Microsoft ADPCM audio data."

-- ACM Driver Details: MPEG Layer-3 Codec  --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 172
    wPid: 9
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x01090191 (1.9.2305)
    fdwSupport: 0x00000001
        ACMDRIVERDETAILS_SUPPORTF_CODEC
    cFormatTags: 2
    cFilterTags: 0
    hicon: 0x0000000067C507A5
    szShortName: "MPEG Layer-3 Codec "
    szLongName: "Fraunhofer IIS MPEG Layer-3 Codec (decode only)"
    szCopyright: "Copyright ⌐ 1996-1999 Fraunhofer Institut Integrierte Schaltungen IIS"
    szLicensing: ""
    szFeatures: "decoder only version"

-- ACM Driver Details: MS-PCM --
    cbStruct: 1804
    fccType: 0x63647561 (audc)
    fccComp: 0x00000000 (    )
    wMid: 1
    wPid: 38
    vdwACM: 0x03320000 (3.50.12800)
    vdwDriver: 0x05000000 (5.0.0)
    fdwSupport: 0x00000002
        ACMDRIVERDETAILS_SUPPORTF_CONVERTER
    cFormatTags: 1
    cFilterTags: 0
    hicon: 0x0000000000000000
    szShortName: "MS-PCM"
    szLongName: "Microsoft PCM Converter"
    szCopyright: "Copyright (C) 1992-1996 Microsoft Corporation"
    szLicensing: ""
    szFeatures: "Converts frequency and bits per sample of PCM audio data."