Get Version Of XP / Accept Particular Serial When Do Reinstall

I have what probably amounts to a stupid question, but I honestly can't recall. I've come across an old system that needs to have windows XP reinstalled, and I'm not sure what disk I'm going to require.The System is an old Dell Dimension 4550, and had an install of Win XP pro SP1 installed on it, and has the sticker stuck to the side of it (with the serial).My question is, before I wipe this thing, I want to make sure I have, or can get a Version of XP that will accept that particular serial when I do the reinstall. I'd hate to bring it down and then find that I can't get it to reinstall with its original XP Key.I have access to pressed/original versions of oem/retail Windows XP SP2 for sure.

I may have a version of SP1 somewhere, but I'm not even sure what type it was, I think it worked with Volume License keys (I'm assuming the actual CDs are different for VL OEM and Retail).My question is, are newer versions such as XP Pro SP2, going to be aware of older serial keys?Would XP SP3 work (I hear it doesn't ask for the key at the beginning but at the end), and if so is there a place where the ISO for XP SP3 is legitimately available?I have a valid XP SP1 key, I just want to make sure I can get it back up after I wipe it.