Buy a laplink cable and laplink that has a dos version, the parallel version is faster but not all pcs have suitable parallel ports,, most do though, it depends on how your CNC is connected, if it uses the parallel port you're with serial unless you also get a parallel switch box.
its about $50 shop around for cheaper versions, cable is about $14, a lot of places sell laplink parallel/serial cables
http://www.laplink.com/products/llv/overview.asp
Guaranteed simplest version is going to be serial, but the parallel is only going to be slightly less easier, if at all, but worth it for the faster speed, really depends on the age of your CNC PC again.
You may even be able to find free software that does what laplink does.
this one seems cheaper comes with 3 cables, but i know nothing about it, and the other PC must have 32 bit windows, so basically anything except dos or windows 3.x ( the machine you will be transferring from, not the CNC machine )
http://www.sewelld.com/PCtoPCFileTransfer.asp
Make your own parallel cable if you feel the need
http://service1.symantec.com/SUPPORT...98121609495725
(also norton ghost can do pc-pc transfer, but its a PITA)