I'm not sure why you'd go looking for IVI Engine 1.83, as all the components needed for our drivers should be installed automatically. When you installed NI-DMM 2.1, did you get any particular error that made you think you needed to get a different IVI Engine?
If the driver wasn't working properly, it might be because of a change mentioned in the NI-DMM readme: "The NI PXI-4070 was upgraded and new revisions of the device beginning with 191485A-01 are incompatible with versions of NI-DMM prior to 2.3. NI-DMM 2.3 and later provides support for all revisions of the NI PXI-4070." You can find the readme by searching "dmm readme" on ni.com, choosing a driver (3.0.1 is what I chose), and opening readme.htm.
To make sure that NI-DMM 2.3 will run LabVIEW 6.1, go back a page (or to ni.com/updates) and search for "DMM 2.3" and click the appropriate link. You'll see that both NI-DMM 2.3 and 2.3.1 support LabVIEW 7.0 or later. Not what you were hoping for, but LabVIEW 6.1 is quite old. You have two options that I can see at this point:
1. Upgrade LabVIEW versions
2. Try to use NI-DMM 2.3 on LabVIEW 6.1.
If you choose option 2, you need to realize that it is completely unsupported. The forums can be a place to seek support, but not many people are going to have experience with or even remember LabVIEW 6.1. If you install NI-DMM 2.3, all the VIs will disappear for versions not explicitly supported. So if you plan to use NI-DMM 2.3 on LabVIEW 6.1, I suggest you copy all of the files and folders dealing with the NI-DMM driver to another location and once you've installed 2.3, copy the files and folders back so that LabVIEW will populate its palettes with the VIs you need.
I hope that helps!
Mark E.
Precision DC Product Support Engineer
National Instruments