Compaq HD Problem

I am having issues on my Compaq. It would not boot without a system disc. I installed a new hard drive, symantec, XP and updated everything. I then tried to install the old HD so I can transfer data but the computer won't boot. Several setups ie. Master/Slave, Slave/Master, both cable select and no jumpers at all and it still won't boot. The last thing I did was add it as an external HD and the computer still won't "find it". All I want to do is get the data on to the new drive. Any suggestions would be appreciated. :confused
Bill