Welcome to the board!
Nobeltec is the leader in pc based marine electronics/navigation software. Not Cheap! Hereís the sounder software:
There isnít any out-of-the-box marine electronics (Furuno, RayMarine, Simrad) that can compete with the quality of what pc software does with traditional sensors, i.e. GPS antenna, radar, transducer, etc.
Click on the 2nd and 3rd screen shots on this page: http://www.nobeltec.com/products/prod_suite.asp
Other pc based software that I am aware of is available from Fugawi and Transas. You might check to see if they sell just a s/w component for sounding.
Fwiw, your pc wonít last much more than a 15.287-seconds exposed to a marine/saltwater environment. You pretty much need to invest in a marine-ized version of a laptop. Donít know what they cost now. Used to be you would add about $1000 over the base price of a pc. All in all, it might be less expensive to toss that RayMarine stuff and get yourself some Simrad toys, since you are in Norway.