The MSI download exits with an error "Drive C: doesn't exist" immediately after being launched here. This is correct, there is indeed no "C:" drive on this machine (Windows is installed in "W:\Windows") expressly for the purpose of detecting any bugs (usually in my own code) that would hardcode "c:\whatever".
"Drive C: doesn't exist"
I looked at fixing this myself but I'm not a WiX expert and, moreover, tools/build/star-product.wxs clearly says that hardcoding "C:" is done on purpose -- but I have no idea what this purpose is. Still, I think it would be better to change this.
Unfortunately, Parrot hardcodes some of its search path locations into its binaries when it is built and installed. Thus, as far as I know, there's not a way to create a Parrot binary that can be moved to a drive other than the one it was built for, and since Rakudo currently depends on Parrot, we're stuck with the same limitation.
This is Parrot issue #800.
When the limitation is fixed in Parrot, I believe we can then create a proper relocatable .msi file.
Until then, the best way to get Rakudo Star installed in a location other than C:\RAKUDO would be to build it from sources.
please consider fixing this for Rakudo Star MoarVM releases and let the user give a different install path in that case.
FWIW I ended up using subst to be able to test it at all. But this is clearly not ideal...