In reply to peas65:
A: You can't "trek" around Aconcagua, at least not what I would describe as a trek. You either have to cross the north shoulder of the mountain itself at a height of about 5800m, or get through some complicated glaciated terrain around the Cerro Cupula area.
B: Many people do indeed refer to a summit attempt on Aconcagua as a trek, but that is a bit misleading to say the least. Aconcagua is a serious high altitude mountain and while it may only be a "walk" to reach the summit it is a walk that often requires crampons and an ice-axe. It is a "walk" for experienced mountaineers, it's not a walk for walkers!