There you are then. XP may feel comfortable but it's holding you back, badly. It simply wasn't designed to make use of modern hardware. At some point security risks, poor hardware support and lack of new drivers will outweigh any familiarity benefits.
I invite you to think of how Windows XP 32 bit has been the most successful Microsoft operating system after DOS. After XP which has been released on 2001 and lasted many years (still officially supported in 2009), we have had 4 new operating systems in 8 years: Vista, Windows 7, Windows 8 and now Windows 10. It shows how the successors were not equally successful hence the need of pushing out new systems.
For my needs, Windows XP works marvelously and I do believe that the incompatibility with modern software is not much a limitation of Windows XP (the only real limit I see is the memory) but rather a marketing choice.
Said that, I am perfectly aware that it cannot last forever but time is proving me right about not getting too comfortable with Windows 7. We are already at version 10. I got myself out of some frustration trying to make things run as smoothly on an operating system that didn't stand the test of time.
If Flat Universe won't run any longer on Windows XP 32 bit, I will of course play it on Windows 7 64 bit.
From a gaming perspective, checking the Steam Hardware poll shows XP to have very little market share. You might want to consider dropping the support for FU. http://store.steampowered.com/hwsurvey?platform=pc