Dual Booting with Win 10 Home & Win XP: Advice needed.

[Term_ite]

I hope someone can send some advice my way concerning my wanting a dual boot system running Win 10 Home & Win XP Pro. At present I only have Win 10 loaded and am shopping for Win XP Pro x64. With the number of options available on Ebay I’m not sure what to buy. I know I want to stay away from purchasing an ISO download and only purchase an authentic Microsoft CD & product key. Hopefully someone can answer the following questions.
1.     Are the updates (the fixes) that were put out by Microsoft back in the day still available somewhere on the Microsoft website to download even though they have ended support for Win XP?
2.   There seem to be 2 choices available when buying the CD & Product Key. One is advertised for refurbishing PC’s c/w key and one is advertised as “Authentic Hologram CD w/ key not a refurbish license”. What’s the difference?
3.   There are also different Service Packs available. One CD is advertised as SP1a, one advertised as “including service pack 2”. In researching this I read a few posts between Geek & Patio in which Patio stated in essence that if you are installing Win XP and it doesn’t include SP1 “you’re in for a fun ride”. I’m assuming that the CD that is advertised as including SP2 would also have SP1 but I seem to remember that XP also had SP3 available. Would SP3 & SP2 still be available for download somewhere on the Microsoft website if I ended up purchasing a CD with only SP1 on it?
Thanks in advance for any help anyone can give me.

[Geek-9pm]

From my own experience.
You can buy a Dell CD of  Windows XP SP3 on eBay for less that $15 from trusted vendors. But you have to have a real product key from a sticker on  Dell  PC. But the 64 bit version is hardtop find. I never have found a low-cost source of the 64 bit version of XP.
Hopetaht is of some help.

[Term_ite]

The worst of it is I have an old Dell PC that bit the dust with XP loaded on the HDD. But the product key is long gone or it never came with it in the first place. I even have the reinstall CD. That's why I have to buy a new key. I've found one that retails for $20 US but it doesn't say what SP is on the CD. That,s why my questions about downloading the different SP's. I found a download for SP2 on the Microsoft site about an hour ago but no luck with SP3. But thanks for the reply anyway Geek. I'll probably be back to pick your brain once I'm ready to install whatever I end up buying.