XP Mode was removed in Windows 8.1 and support for Windows XP Mode Ended in April 2014 alongside support for Windows XP. Its still fine however if you don't connect it to the internet. XP Mode was designed mainly for business use and usually does not have the graphics capability for gaming.
I just received my Inspiron 3847 from Dell.  It has win 7 pro installed (why I bought it), and a win 8.1 pro recovery disc.  Apparently, win 7 pro will run in xp mode easily, as I found info indicating it has an actual copy of xp imbeded in it.  This machine has way more capability than I need.   My question is though, if I eventually use the 8.1 re-install disc, will 8.1 pro run in xp mode?  One site indicates that my computer must support "hyper V", and/or SLAT technology, at a minimum.  My Intel core i5 is supposed to have that capability.  Assuming I have the proper processor, is it worth the hassle setting up 8.1 for xp mode, and is there any thoughts as to how well it would work?  Some instructions for running 8.1 in xp mode go on for pages, and require bios adjustments as well as possible aftermarket software installs, and command prompt (?) inputs.  I'm pretty tech savy, but some modifications can have disasterous consequences. By now I suppose everyone is wondering why I have an interest in doing this.   First, I am 68 and don't like change, with operating systems anyway.  Second, my M.S. flight simulator is not supposed to work well (if at all) with 8.1.  Being my favorite simulator, and the fact no new 8.1 compatible versions have been (and may not be) offered, I may want to stay in the middle ages of xp.  Thanks in for any thoughts.  Art          
Will Windows 8.1 run in XP mode