Thanks for the quick reply.
I do have the /c in there, but it's still not waiting for me.
Here's the line from my script:
shell "%comspec% /c " + Chr(34) + $DriveM + "\2ksetup.exe" + Chr(34)

I know the "+ Chr(34)"'s aren't reallly necessary, they're there for consistency's sake. We've got other executables with spaces in the name.
Maybe the whole thing should be enclosed in single quotes? But it DOES run the .exe, so I would think comspec is OK, its just not waiting.