Whenever I try to use a DXi or VST synth in Sonar 4.0 Home Studio or Music Creator, it makes a fast clicking sound. If I increase the buffer size it gets better, but still not what it should be. I tried Kinetic and it works fine. Strange.
 
Here is what I have running:
 
Windows XP Professional (32bit)
Pentium 4 3.4 HT
Realtek HD Audio which uses MME-32
 
The computer is a HP DC7600. It is sharing an IRQ for the sound, but from what I've read this is normal. I have disabled the other device it was sharing with and the noise is still there.
 
 

Welcome to the forum!

"A fast clicking sound " is a bit strange description because it makes me think of a continuous, stable, rhytmic sound, which isn't typical of driver issues, which I guess is the cause here. You don't have VSTs which are in demo mode, have you? Demo versions of VSTs often make strange noises.

Integrated soundchips are very weak in DAW-work, and MME drivers are the worst there is.
Try downloading the free ASIO4ALL driver and installing it. That might help.