Browser launches at startup, how to stop?

I am a new user to windows 8.1 and am getting more familiar with it each day. I have an issue that I have not been able to resolve however and would appreciate any advice on how to stop this happening. My browser launches immediately after I sign into my windows account on initial boot only, does not happen when it awakes from a sleep condition. It happens regardless of the browser, it happens with whatever the default browser is. The browser opens the local (Australian) MSN page, has a bing search bar, lists all MS services, one drive, outlook.com etc. plus the local news. Bing is not my selected search engine. I was being automatically signed into outlook.com and others but was able to turn off the MS sign in assistant in services. This page is not my set home page.
I have followed the various tutorials on this site and have checked the services, the startup entries, the task scheduler and the registry entries ( great tutorials! Thanks) but it persists. I am at the point of accepting this as part of the "windows experience" but thought it worth a question here to see if anyone has a way to turn it off. Appreciate any help.
Alexm.

Hello

If you go to the following directory on your machine:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp

Are there any files in there? it sounds like you may have a HTML file or internet short cut in there.
Anything in this folder will start up automatically when you log in, delete anything you don't want to start up.

Andrew, thanks for the response. Yes, I have checked that folder, also the startup folders in the "user" directory, no files there. It is proving to be elusive.

I fixed the problem by doing a clean install of windows but did not accept the standard install but used the custom install selecting only the features I needed and was sure of(their function). fixed!