The large orbital rings around Earth are the storage, repair, and recharging pods for the many Protoform Mecha. The rings are surrounded by a powerful force field which makes them impervious to standard Earth weapons, and all Protoform Mecha are programmed to be unable to attack the rings. No one has been able to get inside the rings, so it's unsure if any Windovians are still up there.
Protoform Mecha have no form in their default state, only taking shape when they are bonded to a chosen pilot and are called to their aid. When bonded and called for the first time, a Protoform Mecha takes the shape of something that identifies itself with the personality or traits of the pilot (for example, a dedicated runner might get a mecha which is based on speed, or a boxer might get one that's based on punching). It also reveals to the pilot a number of special weapons (usually 4 or 5) that were chosen based on the form. The special weapons do not include just punching the enemy (though not all Protoform Mecha have hands), but would include standard attacks using an implement (such as shooting a gun, using a sword, etc).
In addition, it also reveals 1 or 2 special abilities of the mecha. These abilities can range from more mundane abilities such as flight, shields or protective barriers, or transformations to more powerul abilities such as after-images. Usually a Protoform Mecha will get either 2 mundane abilities or 1 powerful ability, though it sometimes differs.
When the Protoform Mecha determines that the pilot has obtained enough experience, it will reveal it's true power. This usually unlocks 1 or 2 new "super" attacks, and 1 or 2 new special abilities. The Protoforms are designed to do this to keep their most powerful abilities out of the hands of inexperienced pilots who would be more likely to injure themselves then the enemy.
It should be noted, however, that the weapons and abilities that the Protoform reveals are not so rigid that they're all the mecha is capable of. While an impliment such as a sword is considered to count against the number of attacks a Protoform Mecha has, and techniques such as sword waves as well, a very skilled pilot may be able to develop a new technique using the weapons and abilities they already have that go beyond what is pre-programmed.