Yeah, it seems that this ISO is just the upgrade, and unfortunately it's still quite impossible to find a full install disk anywhere for cheap.

I got contracted to fly halfway across the country to fix a network for an old boss of mine.  I left all my software disks at home because I thought it was going to be just redoing the wiring in the office, but when I got here I found that a few computers were having trouble, and my boss asked me to fix them.  I'm trying to reinstall a Windows XP OS onto them, but like I said I left my disks across the country, and my boss left his in an old storage unit in another state.  I'm currently downloading the XP SP3 ISO from the Microsoft website, but I'm wondering:

When I'm installing with the SP3 iso, will I be able to use the SP2 Product Key Code on the stickers on these machines?  Or am I SOL and need to find an old SP2 disk?