This came up last year with CPU issues and TTax would not install. You can see the threads regarding XP/SP3 and TTax 2013.
Just wanted to share - with the topic including the Pentium III text about this same topic for TurboTax 2014 this year-
I just bought TTax 2014 Premier and installed it on my trusty laptop... Win XP/SP3 with a Pentium III. Was afraid of the new CPU reqs, since the website/box indicate a min req of a Pentium 4.
BUT - it installed today 2/9/2015 - and ran the Updater, opened/imported last years 2013 TTax file, and it all looks good so far...
SO - THANKS - for not updating TTax to use the new SSE2 hardware CPU instruction set, which allows our older processors, like a Pentium III and certain AMD chips to still work with TTax 2014 for this tax season.
I'll have to migrate to my other Win7 laptops for my Quicken 2012 --> 2015 upgrade.