Did you try to manually register the DLL?

You may also want to disable any antivirus that maybe running or at least turn off the runtime features while installing the workstation.

Here are my notes from my last battle with this type error (not an exact match) - www.s-consult.com/.../

The problem is most likely missing pre-requisites when installing Sage 100 Workstation. 

Make sure you are running the Autorun.exe or Setup.exe not the workstation.msi file directly. 

Probably the .NET Framework 3.5 missing but could be missing C++ runtime components also. 

Cancel the workstation install, re-run by selecting Autorun.exe (right-click and choose "Run as Administrator"), then let it install all the prerequisites.