Non starting slk 200k r171

Hi, I put my car away for the winter, after 4 wks I went to start it to find the battery was flat! I replaced the battery with a new Exide 77ah. The car started no problems. i calibrated the door windows as per book. Later I tried to start it again but this time no joy!! Only thing noticed was the cooling fan ran up to high speed? The battery is fully charged all dash lights are present but when turning key to start nothing!
Please can any one help. I have even disconnected the battery and re connected it as this is supposed to reset the system.
Any help would be received with great thanks. Also thanks to JBanks.
Ewrvt.