Ecutalk, Scantech, Conzult and Nissan Data Scan are all good free software. Between them you can do everything you need. My favorite is the paid for NDS because you get GTR dials and it's only ~£30
When you install your usb device make sure the internet is switched OFF. You need to install the FTDI drivers which they provide. Here: - https://drive.google.com/file/d/11o2jz_XCXorhAgoLXTBcG3D_wLy3wbwG/view
If the internet is switched on there is a good chance your computer will try and automatically install the latest drivers which might not be backwards compatible, and it's a pain in the arse to remedy if you are not familiar with FTDI drivers. I would be happy to help if you get stuck...
As well as the links mr b mentioned, Ecutalk here - http://www.ecutalk.com.au/ecutalk.aspx
(copy and paste to browser url) - http://www.ecutalk.com.au/downloads/ECUTalk_v1.3.5.exe
Conzult here - http://www.300zx-twinturbo.com/conzult/index.htm
(copy and paste to browser url) - http://300zx-twinturbo.com/conzult/software/free_conzult.exe
Send us some pictures of your ECU board. Someone will recognize the chips. They will probably be ATMEL ones...
If the chip/ecu is a Calumsult board or Nistune board then you can program it via Nistune software.
If it is a generic ATMEL EPROM chip like mines-ecu etc then you need a programmer to map it... Like this:
Really not worth the hassle when Nistune ecus are only £140.
There's some good pictures in my thread here to give you inspiration if you plan to make a permanent install...http://www.gtir-motorsport-club.com/t6348-nissan-diagnostics-on-windows-and-android