Restart your computer and run the installer again. If that doesn't fix it, follow the steps in the Microsoft troubleshooter: https://support.microsoft.com/en-us/help/10164/fix-windows-update-errors
For Windows 7 users, if the troubleshooter does not help also try this user suggested fix:
UPDATE 2 (suggested by DesignSpark user 'MARK')
For Windows 7.
Uninstall microsoft visual c++ 2008, there might be several in the list.
- Use Windows Installer Clean up.
- Open regedit, find the following key:
- Take ownership and rename it (keep in case of hiccups).
- Now download and install microsoft visual c++ 2008.
- Set 'Windows Module Installer' to manual and start it.
Designspark Mechanical should now install swiftly.
x-UPDATE 1: Microsoft have published a hotfix for this error. Please see: https://support.microsoft.com/en-us/help/970652/error-1935.an-error-occurred-during-the-installation-of-assembly-microsoft.vc90.atl,version
It's a known behaviour of the Windows Operating system to install system updates in the background which could conflict with DS Mechanical's setup process.
If this happens simply restart your computer which will complete any pending Windows updates and then try running the DS Mechanical setup again.