(The problem here could be any of literally dozens of programs, so this answer will not be conclusive, but it should tell you how to find out what the problem is.)
That "disk usage" counter does not refer to how full the disk is, it's how busy it is. 100% busy for 15 minutes is definitely excessive.
From Task Manager's Performance tab, click "Open Resource Monitor". In that display, click the "Disk" tab. This should show you which processes are hitting the disk, and which files are being accessed. This should tell you what programs are the culprits.
Since this is clearly something that is happening at startup time, you might use the "Autoruns" tool from sysinternals.com to investigate everything that is set to start when you boot, or when you log in.
An interesting diagnostic step for these problems is to create another user account and see if the same problem happens there. If it doesn't, the issue is something that is set to start up when you log in (the per-user settings). Autoruns will distinguish between per-user and system-wide startup programs.
capture a boot trace (http://pastebin.com/CYGqRZXE) and share it. Here I can see the DISK activity and which process causes it.
– magicandre1981 – 2015-03-08T08:23:15.983How much RAM? At startup, besides superfetch, there are a number of things thay may happed, like windows checking for updates, antivirus (if any) checking for updates, antivirus (if configured) doing a quick scan – Dan – 2015-03-08T08:58:52.733