Ok, I wrote a batch file today for another person with install problems similar to this post that will install Astro File Manager onto a device that is connected to a computer and mounted as a drive.
Just unzip the folder and then open the unzipped folder and double click on Astroinstall.bat. It will install the apk on the device.
For anyone that knows how to edit a batch file and wants to install a different apk, just place the apk in the folder, and in the right click the bat file and choose Edit.
Look for this line:
adb install ASTRO_File_Manager_2.5.2.apk
replace ASTRO_File_Manager_2.5.2.apk with the name of your apk file.
then save your work and run the bat file. (I always make copies and use the copies in case I screw up.)
Anyway if OP just runs this batch file, he will have access to sd card and can install the ES File explorer and then delete Astro if he wants too.