You can just take the old hard drive and hook it up inside the new computer, be sure to get the correct jumper settings. The old one is likely jumpered to Master, so if its not going on its own seperate IDE ribbon you'll need to set it to slave.
You can buy HDD external case for less than $30 bucks at Compusa and put that HD in the case (very easy to do) Doesn't take a rocket scienist to figure it out. Now you can connect either USB 1 or USB 2. The drive can be used as NAS or SAN for backup.