PC running slow (1 Viewer)

Purchased a PC about 3 weeks ago and since a windows update last week, it takes about 5 minutes between entering the password and launching into windows, once windows is running, it runs completely fine and fast as you would expect, I haven't installed/downloaded anything dodgy etc, Steam is the only thing I've installed so far. The screen just goes blank, during this period with a mouse cursor.

Any ideas on what to do to get it back to launching quickly again?