Harddisk system space

I just formatted a harddisk within Windows XP SP2.
However, go to Computer Management -> DiskManagement

It shows the status of this harddisk is
Healthy(Active) and there are 76 MB reserved system space.

I used this HDD as primary harddisk and now would like to use as data storage so I formatted it, and now it is empty.

Is this normal for the 76MB reserved?

I got another 2 harddisk (there are lots of files inside) in my PC but don't have these reserved system space.

delete both partitions and then format all available space

there should be two partitions to be deleted, once you delete both you will be able to create a new partition using the whole drive

That's normally. Windows reserves about 1% for system space automatically. Besides, when you're talking about 80GB's of free space, will you really miss the 75.5MB?

Well it's almost 25%. While part of that (about 7%) can be attributes to the marketing types at HD manufacturers redefining (see http://en.wikipedia.org/wiki/Gigabyte) what a Gigabyte is, it would appear that something has created a hidden partition. I rarely use disk management build into windows, and use a 3rd party disk tool.

Where are you seeing that just 1 partition exists ? Is this in Windows disk management or when installing the OS ?

I'd use a 3rd party tool to take a look at the thing or even the manufacturers own downloadable tools.