Hi,
It appears to me that are you using Flex Builder 3? If so,
it looks like your path to the Flex SDK 2 is incorrect...
Try this:
compc -locale=it -output=export/es/workspace_rb.swc -source-path
./it "C:/program files/adobe/flex builder 3/sdks/2.0.1/frameworks/locale/
es_ES" -include-resource-bundles alc_wks_client_msg alc_wks_client_trace
alc_wks_client_ui SharedResources collections controls core data effects
formatters logging messaging rpc skins states styles utils validators --
For more details, take a look also in the localization section at the guide at
http://www.adobe.com/go/learn_lc_customizeWorkspace (page 21 for the command and page 36 for the localization steps).
Hope that helps!