1) Open 'Control Panel' folder in 'My Computer' and if needed set to show all contents.

2) Open the 'Dial-Up Networking' 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.

5) Select 'Security' tab and setup exactly as shown below.

6) Dial the ISP using the optimized DUN you have just created. Check that in 'Status/Details' either 'Microsoft compression' or 'Stac compression' is shown under the 'Protocols' entry. If it is not then check that the ISP is in the 'Supports Compression' list in the 'Choosing an Internet Service Provider' page.