After installing Skype on a new machine, make sure it is not running. Then, the chat history from an old installation can be moved to the new installation. The Skype user directories in the new installation need to be replaced with the ones from the prior installation, adding them, if necessary.
C:\Documents and Settings\username\Application Data\Skype\skypeuser
Username is the windows login name under which the given Skype installation will run. Skypeuser is one or more Skype user ids that will log into Skype under the given windows login. If you are using Windows’ Explorer, make sure that “protected operating system files” are shown. (I replaced the entire Skype directory and that also worked).
See Move Skype History From Windows XP To Windows 7, but realize that it says that only the “chatsync” directories need to be copied over… that will not work, however, the entire parent directory (skypeuser) must be copied.