Mathcad 11 is, just like Mathcad 15, a 32-bit application. In principle it should run on a modern 64 bit Windows PC. However there exist (at least) two flavours of Mathcad 11:
Single user, licensed with Cdilla.
Enterprise Edition, licensed with FlexLM.
Cdilla is a nasty licensing system, that installs a software item deep into the OS, combined with a piece of data on a fixed location of your harddisk. On any 32-bit Windows OS there is no problem to install this, in contrast to 64-bit Windows. The OS is more stricterly protected against software wanting to nest stuff deep into its core, and prohibits direct access to the harddisk. The only 64-bit windows OS that allows both these pieces of CDilla to be installed is Windows XP-64. There is NO migration path from Windows XP to other Windows.
On windows Vista, 7, 8 or 10 64-bit Mathcad 11 appears to install without errors, but vital parts of Cdilla are not installed, leading to no reaction upon launching Mathcad. You'll have to look into the logs of windows to find the installation error.
The other problem you have with the Cdilla scheme is that PTC has decided about 6 years ago, to stop the server required for activation. So even if you have a (newly installed) windows10 32-bit, you can successfully install Single user Mathcad 11, but you cannot activate it.
If you have the Enterprise edition, the licensing is FlexLM which is kept up to date and will also run on modern 64-bit Windows. Installing Mathcad 11 Enterprise edition on a new Windows10 64-bit OS should be possible without problems. I don't know if PTC still supports activation though FlexLM licensing..
If you want to (still) run Mathcad 11, you'll have to keep the old machine alive.
Success
Luc
