This is snipped from another thread. I followed it and it worked a dream for me.

I have just installed one of these CA-42 cables today, and I noticed
more than one difference between the installation guide and real life.

This is what I eventually found to work.

I uninstalled any and all Nokia drivers that I found under Add/Remove
Programs.

I uninstalled Nokia PC Suite.

Rebooted machine with NO Data Cable plugged into machine.

Installed Nokia CA-42 driver.

Plugged cable into PC. (Windows did not notice any new hardware added)

Plugged cable into phone. (Windows saw new devices present, and after a
minute or so Windows reported that it had found and installed the drivers
automatically.)

I installed Nokia PC Suite.

I went into connection manager and selected CA-42 only.

From that point on it has worked absolutely flawlessly.

Hope that helps you.

Don