How Do I Flush My DNS Cache on Windows?

1. WinXP: Start, Run and then type “cmd” and press Enter.
2. Vista, Window 7 and Windows 8: Click “Start” and type the word “Command” in the Start search field. ...
3. In the open prompt, type “ipconfig /flushdns” (without the quotes).
4. You should receive a message of your success as confirmation when the cache is cleared

Source:

https://www.noip.com/support/knowledgebase/how-do-i-flush-my-windows-dns-cache/