The worldwide business use of XP was and is very limited. It was never really intended for business use. In fact the operating system used by most UK businesses is Windows 2000 with quite a few still using Windows NT...
The much maligned Windows Vista OS in all its various forms took the best of NT and XP and chucked in a little W2000. Initially a disaster, once SP2 was added it became just as practical as XP. My biggest grouch with Vista and its successors is the fact that in their more basic forms, those versions selected as the de facto OS by computer manfacturers,are country and language specific .
W7 is essentially a combination of Vista and XP.
W8 has proven to be a total PITA for non touch screen users.
Dragging this topic back on thread.... I have three computers in use, 2 on XP and one on Vista; I have no immediate plans to upgrade the OS of any of them. M/S are dropping support for XP end users as of April, but will continue to support and propogate antivirus solutions for the AV producers like AVG, Avast, Norton and MacAfee for a further one year.
The simple solution in the short term for XP end users is to download (and use regularly,) the free antimalware products such as Superantispyware and Malwarebytes in addition to your chosed Antivirus programs.
A 'quick scan' using these sytems takes approx 20 to 30 minutes, a 'full scan' can take several hours depending on how much 'stuff' you have on your hard drive. My computer is my link with the outside world so internet vigilance is important. I run a quick scan using both oof the above systems once a week and a full scan once a month. I also run a full scan once a month using Avast 2014.