I use the Eclipse IDE with the Zend plugin, though I don't know if there is a 64-bit version available. I got it from the Zend website, but I can't remember where I found it >.<
It may or may not be the best choice for you though. Its bloated, but with you're ASP work, I'd suspect it wouldn't be a problem. No graphical form builder though, sorry
What it does require is that you're using the php through a cli. So, that means you'll need the php.exe in a location that it can find in order to run / debug it. Its also a pain to configure for external resources (including the PHP extensions), so things like mysql connections don't tend to work very well until its been configured. You will require the PHP source to compile from, or the php windows installation (I'd go with the .zip and just extract them). You will not require Apache.