|Try safemode. Press F8 on boot and select it|
Scan your pc with malwarebytes and spybot search and destroy. Both are free programs. I have used both for many years. Sometimes one prog finds something the other don't.
Also check your, Program Files>Startup folder and remove all in it
just to make sure it ain't a simple prob.
Also look at your system startups using Spybot - Search and Destroy
Mode Tab > Advanced Mode > Tools > System Startups
Anything RED displayed is worth unticking. (if you need to turn on , for any reason, just tick it again)
Yellow entrys have a look at . Nothing usually bad here but just examine each one.
If your not sure what the program is, google for it (CTFMON.EXE for example)
I am nothing to do with the formentioned Spybot program, just a user. It's very handy in advanced mode and has helped me find problems many a time.
System starup can be a pain when it starts going wrong.
Hope this helps