Apologies in advance for the long winded post!

I have a new base computer, it has no hard disk, so I plan to put my current one in it. Now I understand that this disk will require a complete format and then reinstallation of windows, to allow it to work with the new machine.

So my plan is to backup all my important documents to a slaved formatted 6GB hard drive which I have spare. Once that is done I then format my main hard drive, put it into my new system, reinstall windows, and check everything is running fine. Then I put in my 6GB hard drive containing my files as a slaved drive, and simply copy all the documents on to my new drive. Will this work, or will my new machine not like this hard drive as it has not been formatted?

NB. I intend to backup my most important documents to a CD, just in case.

Thanks in advance for all help.

As far as I am aware yes it should work.
I've only been at this for three months so I haven't tried anything similar yet but from my what I know at the moment I don't see any problems with what you're doing.
Just be sure to make the CD's just in case
Let me know how it works out.

It seems that you are a little confused about what exactly “formatting” means, so I think your answer would be best served by way of an explanation. If you don’t want an explanation, but just an answer, skip ahead to the horizontal line.

A hard disk drive, as I’m sure you’re aware, is a rack of spinning discs called “platters” that hold data magnetically; stored and retrieved by the disk head. Each of these regions are called “clusters” and contain a limited amount of space. An addressing system is then used to reference each cluster. Old drives used CHS (Cylinder-Head-Sector, which is a direct reference to the drive’s geometry, but is limited to around 512MB), new drives use LBA (Logical Block Addressing, which is a linear method with no inherent space limitation.).

In order for an Operating System to efficiently access a hard disk drive, it needs to use a File System, literally, a system for which to store files. This is where things become a little confusing for people. A file system itself does not physically exist on the hard disk drive, it exists in theory only, as data layout format.

If I am an Operating System, and I decide to store a file on a hard disk drive, I basically tell the HDD, via the BIOS, to store a stream of bits in a certain cluster, by passing it the data I want stored and the address I want to store it in. Unfortunately however, each cluster has limited space, so if my file is larger than that sector, I’m going to need to store my data on multiple clusters. This is where I am going to need a system that defines a method of storing files across multiple sectors, that doesn’t mean I have to remember the number of clusters each file takes up. I will need this system to allow me to look up any file based on my own addressing system, and know the length of the file. I will also need a system that allows me to write new files without accidentally over wiring the end or the beginning of other files, and finally, a method to store files in non-contiguous clusters. In other words, I will need a File System.

No matter what system is used however, the actual data on the disk will all just be 1s and 0s. To read that data, all an Operating System needs to do is use the correct method. So that any computer can theoretically read the data on that hard disk, each partition needs to be labeled with the type file system that files have been written in, or in other words, it’s Format. If an Operating System tries to read files using a different method, it will just be nonsense and unusable, because the file system is not in that format.

Formatting is slang for the proceedure of labeling a partition in the desired format (this may be the same format as it was before, it doesn't matter) to another and blanking it by marking all the sectors as empty, in the method used by that particular file system.
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So to answer your question, nothing prevents you from using a hard disk on one PC that has been formatted on another.

Your plan will work fine.