The dd command is essentially just a raw byte copying program. If the "in file" is a disk and the "out file" is a file, it just writes the entire content of the disk (byte-per-byte) into the file. If the "in file" is a file and the "out file" is a disk, it just writes the entire content of the file (byte-per-byte) into the disk. It's that simple.
WARNING: Be careful, dd is a very close-to-the-metal utility, there are no safe guards in that application. It does a pure raw byte-per-byte overwriting of the destination media (disk or file). If you have doubts about what you are doing with it, you probably shouldn't be doing anything with it.
What Mike2K said. I use dd on Linux for this purpose all the time, and it has saved my bacon on more than one occasion when my system drive started to fail. However, as he pointed out, you REALLY need to know what you are doing. If you point it at the wrong disc... Let's just say that "bad things will happen".
I just told you what the write command it. dd is just a copy command, it can copy files, partitions and entire disks. You just specify whatever you want as source and whatever you want as destination, and it will just copy from one to the other. So, there is no "read" or "write" command, there is only a "copy" command. If you want to take a raw image file and copy it to a disk (HDD), then you just specify your file as the source (if) and the disk as the destination (of).
from dd format
This tells me that you have no idea what you are doing. There is no such thing as a "dd format". The dd tool does not write things with some sort of format, it only make a raw byte-for-byte copy of the memory. It ignores file-systems, it ignores formats, it ignores everything and just blindly copies the raw memory from a source (if) to a destination (of). It is entirely your responsibility to make sure you are copying to right things into the right places, or otherwise, you will mess up your system seriously.
re-create a bootable disk
A bootable disk is nothing more than a disk that has a bootloader in its MBR (Master Boot Record). If you have an entire image of a bootable disk (not partition), then writing that image onto another disk should make that disk bootable in the same way as the original one. If you have an image of only a partition of your original bootable disk, then you will need to either install an adequate bootloader on the MBR or take an image of the MBR of the original disk so that you can copy that over to the new disk as well.
That doesn't really matter. Why you would want to do computer forensics under Windows baffles me. But the dd tool, which is mainly a Unix/Linux tool and is probably better used under that environment, can be used in Windows and I don't see what difference it would make, since, as I said already, dd is just a raw memory copying tool, nothing more.
You are looking for an easy way to do what you want to do, but there is no easy way because the tool is not going to do the work for you. The only thing that is hard to do here is understanding what you are doing, and that's not something that dd can do for you.