XP is good os if you have less than 1gb ram.If you have more ram, and you use this. XP supports upto 3GB of ram.
Xp runs all the old version softwares. You cannot expect new version softwares to work in this.
ALso it has direct x9 only. So u can play old games only. But some of the old games can be played only in XP. No doubt in that. games like road rash, blade of darkness, will work only in XP.
Xp is good for laptops. If you use desktop, install more ram and use windows 10 OS.