On having some performance issues with Skype on a fresh install of Windows 7 after some troubleshooting I have found a workaround where I am no longer having any performance issues.
The fix is simply setting the skype.exe processor affinity to use only CPU0.
To do this follow the steps below:
Step 1. Click start and type in “taskmgr” without quotes and hit enter – This should open Task Manager
Step 2. Click the Processes tab (Details on Windows 10)
Step 3. Right click skype.exe and click “Set Affinity”
Step 4. Untick all the boxes except for CPU 0.
Step 5. Restart Skype