Here at home I have a small lan with basically all devices in the main home office being connected via ethernet / cable to one gigabit switch, wlan devices over an apple airport extreme (this one also being connected via cable to the gigabit switch) and additionally an airport express to increase wlan coverage (thick walls).
The main working machine is a laptop with Windows 7 64bit installed, and I have one Windows Home Server (the old, 2003 based one) connected via cable, too. Both have the latest patches applied
Usually I do get quite high transfer speeds from and to the Windows Home Server (WHS) being somewhere around 40-60megabytes per second on large files and slower speeds on smaller ones. All good.
However, sometimes, these speeds drop to one megabyte/second or so and never go back up, opening large folders (with many subfolders/files in them) takes quite long (being a relative term of course, but multiple times longer than usually).
Now originally I suspected that for some reason the wifi card in the laptop would be preferred (despite double checking and also trying to manually set the tcp/ip interface metric high for the wifi card and lower for the gbit/ethernet one), disabling it brought no relief.
What would be the first, next steps to diagnose where this is coming from? What would you do?