Believing in God means a variety of things. To most people it tends to mean just one thing: that one accepts Christianity and a myriad of Christian beliefs and traditions.
It can be a belief that God as a creator, made the world. It is not necessary that a creator God be eternal. After all, men often create things that live long after them.
There are all those attributes of God: omnipotent, omniscient, omnibenevolent (meaning that whatever God dictates is just and true simply because God has defined it as such. A God would have to be very wise to create a universe, but that would not mean that he would necessarily know everything. Seeing into the future goes beyond omniscience, in my mind.
The usual Christian reaction to a statement that I do not consider the Bible to be the divinely inspired word of God tends to cause people to say "well, then you don't believe in anything". Which is quite inaccurate. One can believe in God and not be a Christian, one can believe in God and not believe in any afterlife, one can believe in God and believe in reincarnation, after all.