What is the name of the installer that you are using? Can you check the md5sum of the file that you have and compare it with the ones mentioned on the EPD site? Also, please attach a screenshot of the stage of the installation you are stuck at.
I am currently working with windows 2008 X86. This is the version that is available BBSA81-SP3-WIN32 (8.1.03.312) and i am currently trying to upgrade it to BBSA82-WIN32 (126.96.36.199)
I have attached the screen shot. you can see that in the first screen that it detects the existing Application server and when i select the maintain or update option, it is not directing me to the Setup Type window to select Upgrade. Instead it continues with the fresh install.
What happens when you click Next in the ssecond screen? I think that is how it will work. It will select the upgrade or the fresh install ( 1st image) and then install it.