Solution for Vista unable to connect to XP sharing

METHOD 1: Through Local Security Policy:
NOTE: This feature is for Vista Business, Ultimate, and Enterprise versions
only. For Vista Home Basic and Home Premium see METHOD 2 below.

1. Open Administrative Tools.
NOTE: In Start Menu or Control Panel (Classic View).
2. Click Local Security Policy.
3. In the left pane, click the triangle next to Local Policy.
4. In the left pane, click Security Options.
5. In the right pane near the bottom, click Network security: LAN manager
authentication level.
6. Click the drop down box, and click Send LM & NTLM - use NTLMv2 session
security if negotiated.
7. Click OK.
8. Restart the computer.


METHOD 2: Hack the Registry:
NOTE: This is for Vista Home versions.

1. Open the Start Menu.
2. In the white line (Start Search) area, type regedit and press Enter.
3. Click Continue for UAC prompt.
4. In regedit, go to: -HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Lsa
5. In the right pane, right click LmCompatibilityLevel and click Modify.
NOTE: If it doesn't already exist, create a DWORD value named
LmCompatibilityLevel
6. Set the value to 1
7. Reboot