If this were the Democratic field going into Early 4

[Progressive]

Clinton
Sanders
Warren

What would the results have been in IA, NH, NV, and SC?

[RaphaelDLG]

Do you want an answer more specific than obvious Clinton landslides in all four?

There's a small chance that Clinton would have lost New Hampshire, but I doubt it. 

Without the vaccuum caused by the absence of Warren, Sanders would likely never have gotten the same traction and would have been a minor candidate, with very small/negligible "favorite son coattails" in New Hampshire, probably a third place finisher.

You're going to see a ton of vote splitting between Sanders and Warren of the moveon.org/white liberal crowd, and Warren is only going to siphon off so many Clinton voters (i.e., a handful of the old rich white female ones, and none of the black and brown ones).  Thus helping Clinton immensely.

[Progressive]

I suppose I figured that Sanders would drop out at some point.

[Young Conservative]

Clinton wins Iowa with Warren in Third, Dead heat in NH with Clinton in third, Clinton wins Nevada With warren in third, Clinton obliterates south Carolina with warren in third.
Sanders is a more charismatic figure than Warren in my opinion. He is instantly likable while she isn't.

[HagridOfTheDeep]

Believe it or not, this scenario actually probably helps her keep some of her populist,"WCW" appeal, as no single candidate would have a monopoly on that demographic. She'd emerge from this primary in a much stronger position with a much stronger general election message than she did in reality.

[bagelman]

I suppose I figured that Sanders would drop out at some point.

Warren drops out before Sanders, but Sanders drops out around March-ish and concede's to Clinton's coronation. This is because Sanders never gets the big mo' after having to deal with Warren.

[The Other Castro]

Sanders probably would not have run if Warren had run.

[Mr. Morden]

Clinton vs. Warren with Sanders not running is the more interesting scenario.