And this is the pertinent bit from the msi*.log file:
MSI (s) (D8:2C) [08:28:10:538]: Executing op: ActionStart(Name=VM_InstallVmmon,Description=Installing the vmx driver.,)
Action 8:28:10: VM_InstallVmmon. Installing the vmx driver.
MSI (s) (D8:2C) [08:28:10:540]: Executing op: CustomActionSchedule(Action=VM_InstallVmmon,ActionType=3073,Source=BinaryData,Target=VMInstallVmmon,CustomActionData=5;Win7)
MSI (s) (D8:34) [08:28:10:542]: Invoking remote custom action. DLL: C:\Windows\Installer\MSI26E0.tmp, Entrypoint: VMInstallVmmon
CustomAction VM_InstallVmmon returned actual error code 1603 (note this may not be 100% accurate if translation happened inside sandbox)
Action ended 8:28:11: InstallFinalize. Return value 3.
I had a previous old version that this installer attempted to update. Then when it rolled back, it removed the NEW version, AND the old version. (DOH!).
I've rebooted and tried again, same response. I've deleted all the previous files that I could find in the usual places, and I found a document talking about doing a manual clean of the registry, and I did THAT as well. Still no go.
Any help appreciated!