Doesn't it take a 2/3 vote just to start procedings for impeachment?
I'm not sure what the precise procedural rules are, but when the House moves to impeach it comprises not only the formulation of charges but also the resulting trial. In other words, the trial is authorized by the impeachment. The Senate does not try the president (the House impeachment managers do that) but rather sits in judgment of the trial.
The House motion to impeach initiates the proceedings.
No, it only takes a simple majority in the House to impeach a President. However, it takes a 2/3 majority in the Senate to convict him of the charges in the impeachment articles and remove him from office.
I'm probably not choosing my words very accurately; it occurred to me that the House conduct of the prosecution may be procedural, and arbitrary so far as regards the Constitution. But in any case, as a practical matter I cannot imagine that the Senate would ignore a House move to impeach, and even if they did I would think that the House would ask the Supreme Court to order the proceedings.
I think this is all silly anyhow. GWB is not gonna be impeached. Any scenario in which he were impeached would no doubt result in a Senate trial even if the GOP has control.