Need help with a totally avoidable problem

I've just stated doing volunteer tech support for a local food bank.  Folk
have a heart of gold but  ....

In any case we have two PCs running Windows 2000 pro  (NT).  They can't find
the CDs, any of the documentation or even the 1.44 emergency start up disk.
(if there ever was one)

One system has a proper firewall and AV the other is a 'faith based system'
where in lies the problem

They have some mission critical data on the second (no back up since 3 +
years) AND now have either a system problem or (more likely) mal ware on the
HDD.

I can boot from the CD, from the 1.44 floppy and the HDD under normal
conditions.  What are my options to access the HDD to recover the critical
file?

I have another stand alone PC that I can use that has a good HDD to boot,
perhaps I can set the effected HDD drive up as a slave?

System is connected to the internet via a how brew Ethernet system that is a
kluge of left over equipment but as far as I can tell there is no provision
for file sharing nor do they have any active network servers.

What say ye'all.

FP