|It sounds like you have an ~80gb hard drive, manufacturer's size - that's detected in your bios and in Windows as ~74gb, binary size|
99.9 mb is not ~1 gb, it's only ~.098gb (1,024 mb per gb, binary) . Is that a typo?
A brand name system always, or nearly always, has two partitions on the original hard drive when you first get the computer. The second partition is always smaller than the first one. It used to be the second partition was the Recovery partition, or similar, but I have found that to NOT be the case for at least some more recent models.
On older models the second partition has all the data on it that's necessary to reload the first partition, the partition you see in Windows as C:, with the software that was originally installed on it. In that case the second partition is often called the Recovery partition, or similar. Depending on the brand name builder's preference, the second partition is either normally hidden from you being able to see it in Window's My Computer or Windows Explorer (that's what HP and Compaq do) , OR it's visible in Window's My Computer or Windows Explorer as D but you are prevented from, or are strongly discouraged not to, making any changes to the data that's on it.
I have found that on more recent Compaq and HP notebook models (they were/are about 4 years old or newer) , the hard drive has a second partition but it's NOT a Recovery partition - it's used for something else and is much smaller than that used for a Recovery partition - in that case you get at least two disks that came with the computer originally - a slightly modified full version OEM XP CD, and a CD or DVD with the drivers for the system's devices, and the added programs HP or Compaq provided along with the original software installation . You may also have gotten a third CD to load the feature the second partition is used for.
If you used a procedure that un-hid the second partition, and then wiped the C partition - the larger one - and re-made it, in that case XP's (or 2000's) Setup does NOT assign C to the larger partition - it assigns the NEXT available drive letter after any drive letter already assigned to another hard drive partition that Setup recognizes. C was already assigned to the second partition, after you deleted the larger partition, so in this case the drive letter of the larger partition became D.
If you look in System Information, it says Windows Directory - D:\Windows.
You can change any drive letter assigned to a hard drive partition in Disk Management EXCEPT the one for the partition Windows was installed on, so you can't get Windows to see itself as installed on C rather than D, once it has been installed on D, at least you cannot do that by default, and there are tweaks you can do but you cannot easily do that.
If you run Setup from scratch again after having used something to HIDE the second partition, such as Partition Magic or a freeware equivalent, XP will see itself as being installed on C on the larger partition.
OR , if the second partition is NOT a Recovery partition, the feature installed on it is optional and you may not have been using it anyway or you may not want to use it.
(If it IS only 99.9mb, it's NOT a Recovery partition)
In that case, delete BOTH partitions when you run Setup, then XP's Setup will automatically see itself as installed on C on the first partition when you then make one after that. The first partition does not need to use up the entire available space on the hard drive, in fact it's a good idea for you to make it smaller than that and have at least one other partition on the drive, which you can partition and format after Setup has finished, in Disk Management.
E.g. I have a friend who has a HP Pavilion dv5020ca notebook - it's about 4 years old. It came with three disks.
- a slightly modified OEM XP Home CD, labelled "Operating System CD" "Microsoft WindowsXP Home Edition Service Pack 2"
- a DVD - labelled "Application and Driver Recovery DVD"
- and a CD that's used for loading the feature on the second partition.
The second partition is NOT a Recovery partition, and it's relatively small.
The notebook came with a printed booklet that tells you what the feature is that is installed on the second partition, and how to install it, but I don't recall what the feature is called, and I am no longer working on her laptop. (Although, I could find out what the feature is called and how big the second partition is in a few days when I visit her.)
She lost track of what she did with the original disks, so I ordered a Recovery disk set from the HP web site - via a link in the software downloads for the model - the set I received has the first two disks but not the last one - later on I found all 3 of her original disks.
Another friend's notebook I worked on is a slightly newer (3 1/2 years old?) Compaq model. It's hard drive also has a second partition that is NOT a Recovery partition.