This is what i want to achive with the MPC studio and sonar.

https://www.youtube.com/watch?v=DylihYvYuUI&feature=youtu.be

Brando
Do you have all software installed, current Rev level etc ? ( is this a new unit btw?)
Your manual says the unit is usb powered and midi connected to the pc- is midi by usb or is it a 5 pin DIN plug?
(If 5 pin, what type of midi interface are you using?)

Beepster

Brando
Can you trigger sounds in sonar using the mpc?
Sounds like you need to select the mpc (midi) from the input port list for the track.

This is the likely solution. Read up on how to set up tracks to take external controller messages (so the messages coming from your MPC when you tap the pads) and make them trigger your VSTi program (the softsynth).
 
So click on the MIDI track "input" dropdown menu and look for the MPC. It has to be the MIDI track... not the "Instrument/Audio" track unless you are using a "Simple Instrument Track" which combines the MIDI and Audio tracks into one.
 
The MPC may have multiple "Ports" in which case select the one that the pad messages come from (on my padKontrol there are two ports... one for the pads and another for the knobs... you also have to make sure you have the correct selected in your MIDI Preferences options so select ALL the ports related to the MPC in that dialog). You could also just choose "Omni" in the Input dropdown and the track will accept any incoming MIDI messages from any channel/port on any device (I think) but it's probably better you understand how the input works by choosing the correct device (this will also allow you to use your keyboard for other stuff in isolation to trigger other sounds).
 
You need to also enable the MIDI track's "MIDI Input Echo button" (kind of looks like the "explosive" warning symbol on an aerosol can and will turn blue when it is on). If you had your keyboard working then you have likely already found/used this button before. It is what allows a MIDI track to accept MIDI messages which then get sent to your VSTi (which then playes back the sound).
 
For the "Output" dropdown on the MIDI track you have to make sure it is outputting to the VSTi you want to trigger. In this case it sounds like you have some special MPC synth software you want to use so make sure that softsynth is inserted into the project's "Synth Rack" (that will occur automatically if you used the insert synth dialog properly but check). So click the MIDI track "Output" dropdown, look for the desired softsynth's name and select it (if it isn't already). Now tapping the pads should trigger the synth BUT you may not be able to hear it just yet if your "Instrument" track isn't routed properly. So you'd see it doing stuff but not hear it.
 
In the "Instrument" track (or the audio output section of a Simple Instrument Track... which aren't all that "simple" IMO) you have to go to the "Input" dropdown menu and select the synth you are trying to trigger. This taps the audio output (or one of the audio outputs) of you synth and turns it into something you can hear. If it only has a single stereo output for the whole synth you should see it. It may have multiple outputs for outputting specific sounds (like a drum kit's various kit peices). If you want multiple outs for distinct sounds on a synth that can enable that you need to set up multiple "Instrument" tracks (but you don't need extra MIDI tracks). Probably best to stick to the stereo output for now until you get comfortable with it all. You should also read the user manual for any synths you are trying to using because sometimes they have special procedures for outputting to a DAW.
 
From there the "Instrument" track outputs to a downstream bus like your Master bus (and then out to your sound device(s)) making it audible.
 
So the chain goes like this...
 
MPC Controller > MIDI Track Input > MIDI Track Output > Softsynth VSTi input > Synth VSTi Output > "Instrument/Audio" track Input > Instrument/Audio Track Output > Bus > Soundcard > Speakers.
 
You need to make sure everything along the way in that chain is set to send/receive the messages/audio you want.
 
It may seem complex (and it is a little) but this is why Cake developed the Insert Softsynth Dialog feature. It does most of the grunt work for you but unfortunately does not deal with the MIDI controller input stuff (it can't for obvious reasons). I actually understand MIDi WAY better since I figured out the message/signal chain than when I was using the Insert Synth dialog and actually prefer to set up my own synth stuff all manually (like inserting the tracks and routing them myself).
 
If you get all that setup and everything is working all you have to do to record is press the MIDI track's "Arm" button (make sure it's the "MIDI" track) the activate the Transport Record (by pressing the record button in the Transport Module or by pressing R on your QWERTY keyboard). Then anything you play on the MPC (or any other controller you have set up) will record the live input as MIDI notes and/or controller data into a MIDI clip which you can then play back, edit, etc.
 
Now if you are on the LATEST version of Sonar you're gonna have to watch out because they just introduced a new feature where you can record into the "Instrument" tracks (the audio output from the synth) so those now have record buttons. You need to be able to visually identify the differences between a MIDI track and an Instrument track (and a regular Audio track). If you press record on the wrong one though the track will show a "wave" instead of a "MIDI" clip so that'll tip you off right away.
 
That's all a little long winded but I hope it helps. If anything you can take all the terms and concepts I tossed at you and research them more to get a better understanding of how this all works.
 
Good luck.