The solution to the problem is actually quite easy. The secret is to create the mapped drive before I run the installer (in the Powershell session that is running as Adminstrator) using a Powershell command as shown below.
New-PSDrive –Name “E” –PSProvider FileSystem –Root “\\mylaptop\c$\E_Drive” –Persist
In this example I created a directory called E_Drive on my c drive to act as the E drive. The name doesn't matter.
Now at the Powershell prompt I can access the E drive as if it is an actual drive.