Also check the path environment variable. Just enter path from the command prompt. Make sure it has
C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem
in it. If not, add it via Control Panel, System, Advanced system settings, Environment Variables button. Scroll down to Path in the lower window, select it then click Edit. Be careful not to wipe it out completely as it's allready pre-selected.
On a clean install of Win 7 Ultimate x86, path is set to: C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\