Re: The Seven Horcruxes
We only know for definite the identity of the two Horcruxes that have been destroyed, the Diary and the Ring.
The Locket seems certain but it is not known if this has been destroyed or not, it is assumed that it has been stolen from Voldemort, maybe it is at Grim Old Place, maybe Mundungus has it maybe Aberforth, who knows.
The Hufflepuff goblet seems another good guess but the location is unknown.
I think that the missing Horcruxes are currently both at Hogwarts and are relics of the other two founders.
The Gryffindor relic, I think, is the Griffin doorknocker that is, or was, on Dumbledore’s office door. I think that this can be tied into Voldemort at the time of his visit to Hogwarts to discuss the teaching post.
The Ravenclaw relic, I think, is the tiara that is currently marking the place where Harry hid the Half Blood Prince’s copy of Advanced Potion Making. I also think that this is the same tiara that is referred to as “Aunt Muriel’s goblin made tiara that Fleur is to wear at her wedding to Bill. Very little is said of Rowena Ravenclaw other than that she was “fair” and remembered for her intelligence and creativity. Taking the definition of “fair” to mean good looking, attractive or similar, she may have had something like a tiara. The tiara that Mrs. Weasley refers to is Goblin made, very old and very valuable and could be an heirloom or relic of one of the founders. As I recall the students from Beauxbatons choose to sit at the Ravenclaw table, which may or may not be relevant. I do not know how to tie this into Voldemort other than to suggent that Mrs. Weasley's brothers may be a connection and they were murdered by Death Eaters. A number of contributors to other sites suggest that Aunt Muriel may be a Prewitt.
If I am correct most of the Horcruxes are located where they can easily be found by Harry and his friends if they have access to Hogwarts.