Well i'm going to build a new system, and I want to copy the data from the old HDD to the one on my new system.
I think it's SATA.
So the OS i had on it doesn't matter right?
If I understand you correctly, build your new system including the new drive, install the OS and once the system is up and running then you can copy the contents off your old HDD onto your new HDD and do with what you wish with the old HDD.
Is this your intent?
If you plan on using the so called old HDD for the new system then as mentioned earlier in this post, please ensure to copy all the important off the old HDD prior to using it in your new system.
Hope this helps.