1.8 gig is very small, even for a machine 6 years old.
Because you have formatted the drive, you will be unable to run some diagnostic software, to give the motherboard make and model.
Two things would be worth doing.
1) to take the hard drive out and list the serial number of it.
2) From a win98 startup floppy disk, enter fdisk. Make sure the "y" is selected for enabling large disk support. The pick option 4. This will give details of the disk and any partitions or unused space. It may be that some one has fdisked the drive and not enabled large disk support. This would limit the disk to just under 2.0 gig ( around 1.8gig, does it ring bells? )lol
ps. Do you know the model number of the compaq