Visual Studio Error: "Unable to start debugging unknown user name or bad password" Here is an even better solution than using locolhost with some bugus port. There was a security change in SP1 for Windows 2003 that prevents debugging on anything but localhost. There's an obscure KB article about it here: http://support.microsoft.com/?kbid=896861 The fix is simple: 1. Click Start , click Run , type regedit , and then click OK . 2. In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa 3. Right-click Lsa , point to New , and then click DWORD Value . 4. Type DisableLoopbackCheck , and then press ENTER. 5. Right-click DisableLoopbackCheck , and then click Modify . 6. In the Value data box, type 1 , and then click OK . (reboot may be necessary) If the other computer is truly remote, it will be necessary to define debugging permissions on that machine: Click Start , click Mi...