I have a spare PC (running XP) that has a 160GB (or maybe it's 180GB) hard drive.
Something is wrong with the PC, I get blue screen of death, the previous owners took it into a shop and were told that it couldn't be fixed. So it was given to me for the parts. I already put the internal DVD recorder into my current PC (also running XP) and it works great.
Now I want to take that spare hard drive and add it to my PC so that I have a 2nd hard drive. I think I understand how to hook it up. It is connected by a SATA cable,
And it should be set to be treated as the slave.
But my question is once it is hooked up and I start up my PC, will there be any likely problems/conflicts, like with the systems files that are in that new/slave hard drive?
I don't know if there is a big difference between adding a second hard drive that came from a used PC versus adding a second hard drive that came new/empty from the store.
(beside potential viruses, but I'm not concerned with that)

You shouldn't have problem with booting as long it is set as a slave - your concern will be if your comp will see the added hard drive in control panel, if for some reason comp soes not see HD, shut down PC and change the 2nd srive to CS(cable Select) instead of Slave and restart to see if it can be seen - if you don't get some type of error and have tried both the Slave and Cable Select, it would be the driveand if you do get some error, post results