Today I tried installing the latest version of Wireshark (version 1.2.1 rev 29141) on my Windows 7 x64 laptop. What happened is that installation of WinPcap 4.1 beta5, bundled with Wireshark, failed making Wireshark unusable. What I did next was to go on WinPcap's website and download WinPcap 4.1 beta5. On the downloaded WinPcap's setup file I set it to run in "Vista compatibility mode" and then successfully installed it. At this point on the Wireshark shortcut icon I set Wireshark to always be executed in "Vista compatibility mode" and now this nice network monitor works just fine on my Windows 7 Ultimate x64.