Windows employs a sophisticated DNS resolution strategy that combines interface metrics, network adapter priorities, and DNS server configurations. The system evaluates all available interfaces with these key factors:

// Example of how Windows evaluates interface priority
1. Active interfaces with configured DNS servers
2. Interface metric (lower value = higher priority)
3. Manual DNS configuration over DHCP-assigned
4. IPv4 vs IPv6 precedence based on system configuration

The interface metric plays a crucial role in DNS server selection. Consider this PowerShell snippet to check interface metrics:

Get-NetIPInterface | Select-Object ifIndex,InterfaceMetric,InterfaceAlias | Sort-Object InterfaceMetric

Your observed behavior where nslookup works while other applications fail stems from how Windows handles DNS resolution:

• nslookup: Bypasses the Windows DNS Client service and directly queries specified servers
• Applications: Rely on the DNS Client service which follows the interface priority rules strictly

Here are three approaches to ensure consistent DNS resolution:

// Method 1: Adjust interface metrics using PowerShell
Set-NetIPInterface -InterfaceIndex 12 -InterfaceMetric 10

// Method 2: Force DNS server priority via registry
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters]
"ServerPriorityTimeLimit"=dword:00000000

// Method 3: Network binding order adjustment
netsh interface ipv4 show interfaces
netsh interface ipv4 set interface  metric=10

For complex multi-homed systems, consider these additional controls:

// Disabling DNS registration on specific interfaces
Set-DnsClient -InterfaceIndex 12 -RegisterThisConnectionsAddress $false

// Viewing effective DNS server order
Get-DnsClientServerAddress -AddressFamily IPv4 | Format-Table -AutoSize

Use these diagnostic commands to verify the actual resolution path:

// Display DNS cache entries
ipconfig /displaydns

// Test resolution path
Test-NetConnection -ComputerName www.example.com -TraceRoute

// Network shell diagnostics
nltest /dsgetdc:example.com

Windows employs a sophisticated DNS resolution algorithm that considers multiple factors when selecting which DNS server to query:

// Pseudocode of Windows DNS resolution logic
function selectDnsServer() {
    // 1. Check NRPT rules (for DirectAccess/Enterprise scenarios)
    if (hasEnterprisePolicy()) {
        return applyNrptRules();
    }
    
    // 2. Evaluate active network interfaces
    const activeInterfaces = getActiveInterfaces()
        .filter(i => i.dnsServers.length > 0)
        .sort((a,b) => a.metric - b.metric);
    
    // 3. Apply interface-specific DNS settings
    for (const iface of activeInterfaces) {
        if (iface.dnsServers.length > 0) {
            if (iface.ipv4.manualDns || iface.ipv6.manualDns) {
                return prioritizeManualEntries(iface);
            }
            return iface.dnsServers;
        }
    }
    
    // 4. Fallback to DHCP-provided DNS
    return getDhcpDnsServers();
}

Your Vista scenario demonstrates a classic case where the DNS resolution path diverges between different Windows components:

// Example showing different behavior between nslookup and WinAPI
nslookup example.com  → Uses interface-specific DNS
WinHTTP API calls     → May use different DNS server
.NET DNS resolution   → Might follow different path

When building applications that require consistent DNS behavior:

// C# example forcing specific DNS server
using System.Net;
using System.Net.Sockets;

void ForceDnsResolution(string hostname, IPAddress dnsServer) {
    var request = new DnsMessage {
        Questions = new[] { new DnsQuestion(hostname, DnsRecordType.A) }
    };
    
    using (var udp = new UdpClient()) {
        udp.Connect(dnsServer, 53);
        byte[] response = udp.Send(request.ToByteArray());
        var answer = DnsMessage.FromByteArray(response);
        // Process DNS response
    }
}

For system-wide DNS behavior modification:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters]
"PrioritizeRecordData"=dword:00000001  ; Prefer IPv6
"QueryIpMatching"=dword:00000001       ; Strict interface binding

Essential commands for troubleshooting:

:: PowerShell DNS diagnostic commands
Get-DnsClientServerAddress -AddressFamily IPv4 | Format-Table
Test-NetConnection -ComputerName example.com -Port 53
Resolve-DnsName example.com -Server 8.8.8.8 -DnsOnly

To adjust interface priority programmatically:

// C++ example modifying interface metrics
#include 
#include 

void SetInterfaceMetric(DWORD index, DWORD metric) {
    MIB_IPINTERFACE_ROW row;
    InitializeIpInterfaceEntry(&row);
    row.InterfaceIndex = index;
    row.Metric = metric;
    SetIpInterfaceEntry(&row);
}