Also, Dean, I am using 7.6 client on Windows 7 and it laggs like hell? How can I fix it?
Try updating your graphic card drivers. To do so you need to know the manufacturer and the model of the card. Then find the manufacturers site and look for updates for the correct model. Its probably under 'support'. Another thing you can do is to use fullscreen while playing and close programs like spotify and steam.
Im not sure if it has any effect with windows 7 but you can try to open properies for tibia and change 'compatible with' to windows xp (or any other that seems to lagg less for you).
Finally, try which laggs the least for you looking what fps (press alt+f8). If you have anything above 30 you're good enough, then its probably you connection/the server host.