1) Open the 'Control Panel' folder in 'My Computer'.

2) Open the 'Network and Dial-up Connections' folder in 'Control Panel'.

3) Edit the DUN you wish to 'optimize' by selecting it and choosing 'Properties' as shown

4) Select 'Networking' tab and setup exactly as shown below. You may find that removing QoS support helps with your connection, highlight "QoS Packet Scheduler" and click on "Uninstall" then "OK" for any prompts that follow.

5) Select 'Settings' and setup exactly as shown below, click 'OK' and exit.

6) Select 'Advanced' tab and under 'Internet Connection Firewall' untick 'Protect my computer and network by limiting or preventing access to this computer from the Internet'. NOTE: This will disable all firewall protection, if you are at all concerned then re-enable this option.

7) Select 'Configure' from the 'General' tab.

8) Make sure that you have setup and optimized the COM port as shown here. Select '115200' under 'Maximum speed(BPS)' if you have problems lower this to '57600'. Untick 'Enable error control' and 'Enable modem compression', make sure that 'Enable hardware flow control' is ticked. Select 'Okay' and exit DUN setup. 

IMPORTANT: If you experience problems when online try ticking the 'Use error control' option to enable error control again. If your ISP does not support MPPC compression then you MUST tick the 'Enable Modem Compression' box

9) Open 'Phone and modem options' in the 'Control Panel'.

10) Select the 'Modem' tab and highlight your modem, then select 'Properties'.

11) Select the 'Advanced' tab and enter any strings you wish to use from the Modem strings section.

12) Dial the ISP using the optimized DUN you have just created. Click the network icon in the lower right of the taskbar and check that 'MPPC' is shown under the 'Details' entry. If it is not then check that the ISP has 'MPPC Compression'. NOTE: If your ISP supports Microsoft MPPC compression and you are not getting 'MPPC' or cannot ping servers then try enabling 'Error Control' in Step 8. If you still cannot negotiate 'Microsoft compression' / MPPC compression' then enable 'Enable Modem Compression' in Step 8.