I'm running a free office suite called Open Office,
I use Open Office for my model railroad inventory. I have one list per calendar year, and a master list that is a joining of all the years.
I have the columns:
Scale -
Manufacture -
Manufacturer's Line -
Stock Number -
Description -
Classification - Locomotive, Freight, Passenger, MOW, Head End, part, tool, reference, consumable, structure, scenery, control, power
Road -.
Paint Scheme -
Road Number -
notes - I use for special notes like decoder equipped, coupler type, sound, etc ( These should probably all be broken down into their own columns )
Cost -
Date of purchase -
Where Purchased -
Disposition - what happened to the item (sold, given away, lost, destroyed, consumed, used for model x)
I also have columns for original retail, current market, high, and low, but never have time to keep those up to date.
The whole thing could be better like including an AAR designation for the freight cars, condition of the item, and as noted above what type of decoder, what channel it is on, voltage of light bulbs, what type of couplers, last inspected date, certified for museum operation, certified for club X, operation, etc.