When you chat with someone on Skype, everything that you chat about is being stored in special files. These files are on your computer (unlike your Skype contact list for example, which is stored on Skype servers). This is why you can browse through the old messages later, but only from your computer. If for any reason you need to delete your Skype chat history, then follow these steps:
- It is recommended to first backup your contacts (sometimes they disappear). After that quit Skype.
- Open any folder or Windows Explorer.
- In the top part of the window in the address bar input %appdata%\skype and press Enter.
- Now open the folder with the same name as your Skype name. Inside delete everything except the config.xml file.
This action will delete all your chat history and keep your Skype settings. Keep in mind that chat messages (that you send to someone) are stored not only on your computer but on the computer of the person that receives them as well.
Also I want to mention that there is another way to delete the history from inside the Skype options but then the actual files remain, therefor the history can still be accessed (you just don’t see it in the program).