First of all, I'm a 'newbie', so when I had computer problems, an acquaintace reinstalled XP for me from what he said was an unopened disk. Well, it turned out to be a Dell disk that needs to be activated, but I don't have a key, and now don't know what to do. What are my options?
That is the "unattended" key used in OEM XP's to get through installs. It will not Activate. And, I don't believe for a minute that any "generated" key will work. OEM keys have a different makeup.
You are going to have to buy yourself a Retail version. I've seen Home for around $60. If you must have Pro (which a personal pc doesn't need), I've seen them for $75. If you buy it on ebay, make sure it's not used - has to be new.