You are using the factory sound card. That is the problem.
 
Factory cards generally use MME as the driver. It works ok, most of the time with AUDIO but not so much with MIDI.
 
In midi, the softsynths need better processing than the factory card can offer. As a result, the card is trying hard to process the midi, send it to the synth, and get the audio output back to the speakers in a timely manner. The result is what you are hearing..... bad buffering that sounds like choppy tempo.  The more synths you have, the worse it gets.
 
You can try changing the buffers and latency settings. Most often, with MME, when you fix one issue, something else becomes out of balance.  Another option is to try ASIO4ALL which sometimes works well enough to give some halfway decent performance to the playback.
 
HOWEVER.... if you want to solve the problem and do it the right way.... buying a third party external USB based interface is the way to go. Everyone who takes up home recording as a serious hobby or more..... ends up with a nice interface at some point. One that uses the native ASIO drivers without need for wrappers like ASIO4ALL or special codecs.
 
No matter how nice the computer, or how powerful it is, the factory sound card is simply NOT up to the task you are asking it to do when using Cakewalk software.
 
Have a look at some of the users here (in the signatures most of the time) to see what soundcard/interface we are using. Look around and know what you are needing BEFORE you spend your money because all external interfaces are NOT the same. Some use proprietary codecs and are gimmicky, while others are rock solid workhorses that will do a fine job no matter what you throw at them.

Welcome to the forum.
Check out the Help file sections on Improving Audio Performance and Troubleshooting.
Increase the MIDI Buffers. Increase the Latency, which will reduce the strain on the processor, and since you're not recording instruments live, there's no need for minimum latency.
It's possible that your old laptop had a 7,200 rpm HD and your new computer has a 5,400 rpm drive. Plus, newer computers with Win 7 or 8 will probably have more bloatware than older machines, possibly reducing peformance.
A dedicated audio interface connected via USB or FireWire will greatly improve your ability to work in MC or any DAW.

No.
 
Please do yourself a favor and get a decent USB sound card.  Focusrite, M-Audio, Presonus, etc are more in line with the kind you should be looking at. Those "cord based" usb things generally use codecs and do not run native ASIO and as a result, do not work as well as you need them to do.
 
If money is the issue for affording a decent interface, please take the time to save the money for the purchase or check on Ebay for a used one. You can often find good used gear at 50% less than the cost of a new one. I have several used pieces of gear in my studio....they work fine so who cares that I got them on the cheap side....?   As long as they work..... that's all that matters.

Thanks for your advice guys! I ended up getting a steinberg interface that costs about $100. It works great for what I do. I still have no idea what it does, or how it's doing it, but it works.
 
I appreciate your time!
Don