This is my current PROM/EPROM programming setup.

I have a DELL Inspiron 8000, Running Windows 2000, with a Parallel and Serial Port.
The Parallel Port connects to the Needham's Electronics EMP-20.
For erasing I have an ANGO LA6T EPROM Eraser

I have had the DELL and the EMP-20 for a while, just recently got the ANGO

Today I read an 27C512 EPROM into the EMP-20's Buffer and Save it to a file. Then took a Blank 27C512 and Programmed it from that saved File. Then exited the EMP-20's program, and restarted it, then loaded the saved file, then did a Verify Buffer on the Original 27C512 and the formally blank 27C212. Both Passed. Then I erased both 27C512's and tested them with the EMP-20 for being Erased, both passed..

I have to conclude that the EMP-20 and the ANGO are working correctly.