The Windows 7 ERD (Emergency Repair Disk) Is some tool items on a bootable disk. It is not tied to a licence, it does not hold passwords, it is just a short disk that can be used to attempt a few fixes. It is not any more specific to the computer, than an install disk is. The OS Install disk itself has the same repair things in it, assuming it is available and still functional.
64bit vrses 32Bit , not compatable, would need 2 different disk items when the systems are different.
That is a Yes :-) it is a generic item the same functions in it as any other.
DART and ERD commander, I did not cover.
A full image backup of Each of the "systems" is IMO more valuable than a bootdisk that can patch up and retract a few things. Software used to make and restore an image should Also be the type that operates outside of the system, so you can do a recover when the system is unbootable.
There exist also many Bootable disk assemblies/compilations of software that would be recommended in case of having to repair the system from outside the system, If you searched for , what is the best boot disks that can be used to access and repair the system, you could find them.