|If XP is still working....|
Look at the original hard drive in Disk Management.
Control Panel - Classic View - Administrative Tools - Computer Management - Disk Management.
Does the hard drive have a smaller second partition on it ?
If it does, what is the size of it ?
If it does not have a second partition, or if it does but it's too small (e.g. smaller than ~ 1 gb), you do not have a Recovery partition that has all the data on it needed to reload the original contents of the larger partition seen as C in Windows.
Examine the mboard. The mboards used in Northgate systems usually have a Syntax model number on them, probably on a stuck on label. e.g. P4S651M.
That model number can be used to determine which mboard model you have.
In most if not all cases, Northgate used mboards that are the same as retail versions of mboard models with a Northgate bios version on them, and in that case a mboard manual and drivers for the mboard can be easily found.
E.g. Syntax P4S651M mboard = AOpen S651M
In the case of your Northgate STAX2517C system, when I searched yesterday with: Northgate STAX2517C
I found from the few "hits" that you have a Socket A (Socket 462) mboard and an Athlon XP cpu, but not much more.
Microsoft Windows XP Home Edition Version 2002 Service Pack 2
704MB of RAM
AMD Athlon(tm) XP 2500+
768mb of ram in the mboard - 64mb used by the onboard video = 704mb.
Northgate STAX2517C Desktop PC w/ AMD Athlon XP 2500+