Take it easy, don't jump at ones on fllashing the device, but first install the pcsuite software and just insert your phone on one of USB ports and select as syncronising device and let it instal the phone device driwers and after is finish installing pull USB out few sec then put it again on the same USB port but select as Storage driver, and let it install drivers...then prepare your fllashing operation.
I might guess..that your phone allready was fllashed with "zimage" for nitdroid that's why you are getting the warning on screen, weell fllashing it again it will vipe that duo boot...but is up to you...
I see by the product version...you are atempting to update, and local version is 001 as you see on firmware file...don't use higher value than that.
Try this way...to make it easy fllashing your phone, maybe you should make dir in c:/nokia and install fllash in there and import your firmare.bin in that c:/nokia/fllasher and in comand line on dosbox-win enter like this:
c:/nokia/fllasher/fllasher.exe -f -F c:/nokia/fllasher/firmware.harmatan_001.bin and turn your phone OFF.
I did fllash my phone by turning on instead bcz pc could not find my phone few times...so it might happen to your phone to...so try borh ways...but careful do not disconect cable if pc and phone are active and operating fllashing or transfering files!