Microsoft sucks. Here's how to re-enable what they disabled on your computer, to keep it from talking to non-Microsoft computers.

Enable Authentication in Vista Home Edition

1. Start the Registry Editor by selecting Start, All Programs, Accessories, Run.
2. In the ‘Open’ field of the Run dialog box, type regedit and click the ‘OK’ button.
3. The User Account Control system will ask for permission to continue. Click the ‘Continue’ button.
4. In the Registry window, expand the following:
   1. HKEY_LOCAL_MACHINE
   2. SYSTEM
   3. CurrentControlSet
   4. Control
   5. Lsa
5. In the ‘Value’ pane of the Registry Editor, check to see if the following DWORD exists: lmcompatibilitylevel (note: that word is LMCOMPATABILITYLEVEL in lower case letters, not 1m or Im). If it does, perform the following:
   1. Right-click lmcompatibilitylevel and select ‘Modify’ from the pop-up menu.
   2. Enter a Value data of 1.
   3. Click the ‘OK’ button.
6. If the lmcompatibilitylevel DWORD does not exist, create a new DWORD.
   1. From the Registry Editor menu, select Edit, New, DWORD (32-bit) Value.
   2. A new DWORD called ‘New Value #1’ will be created.
   3. Rename the new DWORD to lmcompatibilitylevel.
   4. Right-click lmcompatibilitylevel and select ‘Modify’ from the pop-up menu.
   5. Enter a Value data of 1.
   6. Click the ‘OK’ button.