Hiro probably can't freeze Peter because since Peter has access to Hiro's powers, he can probably be active during Hiro's time freezes. I seem to recall him surprising Hiro like that once in the first season.

He probably also doesn't want to kill Peter, and just plans to explain things later. Since Peter will recover from any thing Hiro does to him (short of chopping off his head, or so Adam suggested), he can remove Peter as an issue without risking permenant damage.

Ultimately, though, it just comes down to "Hiro vs. Peter: HEAVEN OR HELL! FIGHT!" Which is cool by me. I just wish Peter had better control of Hiro's powers so they could do all sorts of fancy time trick powers. Get some Deja Fu going on, to borrow a term from Discworld.

Remember what happened the last time Heroes hyped up a big fight?

You mean the finale? Yeah, and that worries me some too, since the main problem with the finale....and really with any episode of Heroes, is the budget. They just can't afford to show fancy superpowers all the time, and I'm sure the budget they've got isn't piffling to begin with. But Hiro's power isn't a budget-drainer like some of the others. You don't need CGI, you don't need a green screen, and you don't need cranes....just some trick photography and fancy cuts. So I hold out some hopes.

Peter really should use his powers properly now and just read people's minds to know if they are telling the truth like Adam or Hiro for example. He's already healed his memory so he knows what he has and he has Sylar's inuitive understanding of how things work (even if he doesn't know it) which seems to be a passive ability so he can use that too.
Sylar can clearly use it in conjunction with acquired abilities because he always instantly knows how to properly use the power and is usually better at it than the person he took it from (ie Telekinesis and Brian Davis) and since he didn't know he had the power it's clearly useable without him trying.

I agree, there are stories of people who survived gunwounds in their head.

What I don't understand though is how Peter is stupid enough to act like this. I think it's pretty obvious if he does the things people force, lead or manipulate him to do, it will eventually end up in an unchanged future. He should figure out by now, that changing the future is more a matter of not following the obvious way.

Well, point blank blast from a shot gun? A slightly (slightly!) greater chance of removing your head from your body than a pistol.

(Don't worry, I felt the same as you, but me and a friend came to the above conclusion about how it works.)

I don't remember Adam's exact line, but couldn't he have meant that they "couldn't kill him" because they still needed him for something? Like that they wanted access to his blood for its curative properties or something?

It is possible that he's just become such a Badass Regenerator because of how long he's had to master it that he's way beyond Claire and Peter, I suppose. Any way, how would he know he couldn't heal it? Obviously he couldn't have tested it on himself. Unless he's encountered other Regenerators during his time.

Also: we know Claire and Peter can regenerate from brain injuries as long nothing is stuck in there. Claire had that stick and Peter had that shard of glass. But we also know that Claire would've been Dead For Reals if Sylar had eaten her brain...

...I think that it's probably best to just go with Bellisario's Maxim on this one, guys. Just like with comic books--Deadpool can regenerate as much as (and no more than) the current writer needs him to. Claire, Peter, and Adam are the same.

well i mean the woman held the shotgun to his face and said "shoulda done this a long time ago.................." so i would imagine it applies to him and not just peter.  i do not know why they didn't simply kill him though, if they all knew all that was required was decapitation/shooting him in the head or face or whatever.  he mentioned earlier that if they could've killed him, they would have, so i guess maybe she was the only one that knows and the rest of the company did not realize what was necessary???? that is sort of dumb though, because you'd think that with all the ways they apparently tried killing him, that would be one of them.  it seems like the most obvious one.

also, bringing PERSONX let us call him back from the death is pretty gay.  i wish they'd left him dead.  i don't like it when television/movies milk emotionally charged moments only to have them have zero in the way of lasting repercussions.