How much weight can an upstair room can hold?

Semi,
I would check the distance between joists if I were you.
They used 24" centers alot and the joist is usually a true 2X6 in older houses. Today it's 16" centers and the joists are 1.5"X7.5" at best. The issue is, will 24" centers with 2’X6”s hold enough weight? Maybe, but when I remodeled my 3rd floor they made me add joists between the existing joists and onto the existing bowing 2"X6" joists to bring it up to code.

No problem.. But if you line the walls floor to ceiling with LPs.. At about 4,000 equals a ton..
I knew a guy who was evicted because his 30,000 LP collection was causing the ceiling in the apt below to crack open from the joists sagging.

Thank you, guys and thanks to a friend who warned me. Yes, I just now notice a crack about 6 " on the ceiling of the garage where I have put my main rack on the carpet floor in the room above . I wonder what kind of house Kimball Hills built but the house is less than 10 years old and it ain't a cheap one either. It 's time to get busy to pack all the gear and gets rid of them at a loss a again. Time to get ICE stuff. It's just a story of my bad luck.

1 crack is not a problem. Cracks happen throu out the life of a house. They happen as the house settles. Watch the crack and see if it gets longer and you could also have someone come and look at it. No reason to get rid of anything.

Hevac1 is correct. one thing you can do is use some tape to mark the ends of the crack to see if it is elongating. Elizabeth is correct about storage of LPs, but 500 lbs of gear should not be a problem at all. Also consider where the gear is located. If its arrayed against a load bearing wall and spread out so its over several joists, then the load on any one joist is small and transferred to the vertical load-bearing studs and plates that are designed to carry much bigger loads. If you are really worried about this, call an architect or structural engineer. Would be well worth a couple of hours of their time (if they charge you at all; they may be able to answer this question very quickly in a brief phone call) considering the cost and hassle of selling all your gear.