I go with excel for now.
I'd love to use some sort of software but I'm too cheap to pay for it when excel does it for free and I'm an accountant so I use excel for everything!

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I can't see an insurance company accepting an excel spreadsheet or even simple photos, especially with UGCs.
For example,
I just cased my copy of Flintstones 2 last night and it's on my shelf now with the rest of my cased NES games. I'm sure the insurance company would want a photo of the actual cart in my possession since anyone could just print out the cover and throw a UGC up on a shelf with no game in it.
That's why I like the pickups thread we have on this site. It would be a bit stronger proof that I am actually acquiring items for a collection.
I've considered insurance too but the documentation required to actually get paid out would probably be a lot of work.
If I ever was robbed or had a fire or something I'd just be happy with everyone being OK.
Games can be replaced.