Problem upgrading WMS from 1.3 to 1.4.1

I'm trying to upgrade WMS on Windows Server 2012 64-bit from v1.3.0.40983 to v1.4.1 but am stopped in my tracks by the following error message:

"Dell Wyse Management Suite (WMS) v2.0.80.4 is detected. Upgrade from this version is not supported. Setup will abort now."

Can anyone offer advice?