Clarion 7.3 renamed the DLLs from C70* to CLA*.
So there are no more C70NET Dll, it's now called CLANET.DLL.
There is a bug in Clarion 7.3 though, if you install it on top of 7.2, where it complain after the link, that C70NEt.DLL is unavailable for copy. You can ignore that. If you want it to go away, delete your SoftVelocity settings, and re-install 7.3.
If you get errors when removing C70Net from your project tree, then unregister the NetTalk template, and re-register it.
cheers
Bruce