--- a/build-msw.txt
+++ b/build-msw.txt
@@ -12,12 +12,8 @@
 Compilers Supported
 -------------------
 MinGW GCC (recommended)
-
-MSVC 6.0 SP6: You'll need Boost version 1.34 because they dropped support
-for MSVC 6.0 after that.  However, they didn't add Asio until 1.35.
-You should still be able to build with MSVC 6.0 by adding Asio to 1.34 by
-unpacking boost_asio_*.zip into the boost directory:
-http://sourceforge.net/projects/asio/files/asio
+http://tdm-gcc.tdragon.net/ has an easy installer.  Go back a few versions
+for a little older gcc like gcc 4.4.?.
 
 MSVC 8.0 (2005) SP1 has been tested.  Note: MSVC 7.0 and up have a habit of
 linking to runtime DLLs that are not installed on XP by default.

--- a/headers.h
+++ b/headers.h
@@ -70,6 +70,7 @@
 #include <boost/filesystem/fstream.hpp>
 #include <boost/algorithm/string.hpp>
 #include <boost/thread.hpp>
+#include <boost/interprocess/sync/file_lock.hpp>
 #include <boost/interprocess/sync/interprocess_mutex.hpp>
 #include <boost/interprocess/sync/interprocess_recursive_mutex.hpp>
 #include <boost/date_time/gregorian/gregorian_types.hpp>

--- a/init.cpp
+++ b/init.cpp
@@ -244,8 +244,7 @@
     // Required to protect the database files if we're going to keep deleting log.*
     //
 #if defined(__WXMSW__) && defined(GUI)
-    // todo: wxSingleInstanceChecker wasn't working on Linux, never deleted its lock file
-    //  maybe should go by whether successfully bind port 8333 instead
+    // wxSingleInstanceChecker doesn't work on Linux
     wxString strMutexName = wxString("bitcoin_running.") + getenv("HOMEPATH");
     for (int i = 0; i < strMutexName.size(); i++)
         if (!isalnum(strMutexName[i]))
@@ -257,7 +256,6 @@
         unsigned int nStart = GetTime();
         loop
         {
-            // TODO: find out how to do this in Linux, or replace with wxWidgets commands
             // Show the previous instance and exit
             HWND hwndPrev = FindWindowA("wxWindowClassNR", "Bitcoin");
             if (hwndPrev)
@@ -281,8 +279,18 @@
     }
 #endif
 
+    // Make sure only a single bitcoin process is using the data directory.
+    string strLockFile = GetDataDir() + "/.lock";
+    FILE* file = fopen(strLockFile.c_str(), "a"); // empty lock file; created if it doesn't exist.
+    fclose(file);
+    static boost::interprocess::file_lock lock(strLockFile.c_str());
+    if (!lock.try_lock())
+    {
+        wxMessageBox(strprintf(_("Cannot obtain a lock on data directory %s.  Bitcoin is probably already running."), GetDataDir().c_str()), "Bitcoin");
+        return false;
+    }
+
     // Bind to the port early so we can tell if another instance is already running.
-    // This is a backup to wxSingleInstanceChecker, which doesn't work on Linux.
     string strErrors;
     if (!BindListenPort(strErrors))
     {

--- a/net.cpp
+++ b/net.cpp
@@ -20,7 +20,7 @@
 //
 bool fClient = false;
 uint64 nLocalServices = (fClient ? 0 : NODE_NETWORK);
-CAddress addrLocalHost(0, DEFAULT_PORT, nLocalServices);
+CAddress addrLocalHost(0, 0, nLocalServices);
 CNode* pnodeLocalHost = NULL;
 uint64 nLocalHostNonce = 0;
 array<int, 10> vnThreadsRunning;
@@ -1006,7 +1006,7 @@
 
                 // Randomize the order in a deterministic way, putting the standard port first
                 int64 nRandomizer = (uint64)(nStart * 4951 + addr.nLastTry * 9567851 + addr.ip * 7789) % (2 * 60 * 60);
-                if (addr.port != DEFAULT_PORT)
+                if (addr.port != GetDefaultPort())
                     nRandomizer += 2 * 60 * 60;
 
                 // Last seen  Base retry frequency
@@ -1185,6 +1185,7 @@
 {
     strError = "";
     int nOne = 1;
+    addrLocalHost.port = GetDefaultPort();
 
 #ifdef __WXMSW__
     // Initialize Windows Sockets
@@ -1236,12 +1237,12 @@
     memset(&sockaddr, 0, sizeof(sockaddr));
     sockaddr.sin_family = AF_INET;
     sockaddr.sin_addr.s_addr = INADDR_ANY; // bind to all IPs on this computer
-    sockaddr.sin_port = DEFAULT_PORT;
+    sockaddr.sin_port = GetDefaultPort();
     if (::bind(hListenSocket, (struct sockaddr*)&sockaddr, sizeof(sockaddr)) == SOCKET_ERROR)
     {
         int nErr = WSAGetLastError();
         if (nErr == WSAEADDRINUSE)
-            strError = strprintf("Unable to bind to port %d on this computer.  Bitcoin is probably already running.", ntohs(sockaddr.sin_port));
+            strError = strprintf(_("Unable to bind to port %d on this computer.  Bitcoin is probably already running."), ntohs(sockaddr.sin_port));
         else
             strError = strprintf("Error: Unable to bind to port %d on this computer (bind returned error %d)", ntohs(sockaddr.sin_port), nErr);
         printf("%s\n", strError.c_str());
@@ -1278,7 +1279,7 @@
                 printf("host ip %d: %s\n", i, CAddress(*(unsigned int*)phostent->h_addr_list[i]).ToStringIP().c_str());
             for (int i = 0; phostent->h_addr_list[i] != NULL; i++)
             {
-                CAddress addr(*(unsigned int*)phostent->h_addr_list[i], DEFAULT_PORT, nLocalServices);
+                CAddress addr(*(unsigned int*)phostent->h_addr_list[i], GetDefaultPort(), nLocalServices);
                 if (addr.IsValid() && addr.GetByte(3) != 127)
                 {
                     addrLocalHost = addr;
@@ -1306,7 +1307,7 @@
                     printf("ipv4 %s: %s\n", ifa->ifa_name, pszIP);
 
                 // Take the first IP that isn't loopback 127.x.x.x
-                CAddress addr(*(unsigned int*)&s4->sin_addr, DEFAULT_PORT, nLocalServices);
+                CAddress addr(*(unsigned int*)&s4->sin_addr, GetDefaultPort(), nLocalServices);
                 if (addr.IsValid() && addr.GetByte(3) != 127)
                 {
                     addrLocalHost = addr;

--- a/net.h
+++ b/net.h
@@ -12,7 +12,7 @@
 
 
 
-static const unsigned short DEFAULT_PORT = 0x8d20; // htons(8333)
+inline unsigned short GetDefaultPort() { return fTestNet ? htons(18333) : htons(8333); }
 static const unsigned int PUBLISH_HOPS = 5;
 enum
 {
@@ -150,11 +150,11 @@
         Init();
     }
 
-    CAddress(unsigned int ipIn, unsigned short portIn=DEFAULT_PORT, uint64 nServicesIn=NODE_NETWORK)
+    CAddress(unsigned int ipIn, unsigned short portIn=0, uint64 nServicesIn=NODE_NETWORK)
     {
         Init();
         ip = ipIn;
-        port = portIn;
+        port = (portIn == 0 ? GetDefaultPort() : portIn);
         nServices = nServicesIn;
     }
 
@@ -185,7 +185,7 @@
         nServices = NODE_NETWORK;
         memcpy(pchReserved, pchIPv4, sizeof(pchReserved));
         ip = INADDR_NONE;
-        port = DEFAULT_PORT;
+        port = GetDefaultPort();
         nTime = GetAdjustedTime();
         nLastTry = 0;
     }
@@ -193,7 +193,7 @@
     bool SetAddress(const char* pszIn)
     {
         ip = INADDR_NONE;
-        port = DEFAULT_PORT;
+        port = GetDefaultPort();
         char psz[100];
         strlcpy(psz, pszIn, sizeof(psz));
         unsigned int a=0, b=0, c=0, d=0, e=0;