As of today, Microsoft will no longer support 12-year-old operating system Windows XP. No further technical assistance or updates will be offered, which potentially means any new security breaches or viruses will go unchecked. Potentially, then, Windows XP users will be at risk.
Many video games already side-step Windows XP in favour of newer Microsoft operating systems, and presumably will do so as a matter of course from here on out. If you're running a PC with XP, chances are it's too old to handle most games anyway. Time for an upgrade. Maybe you could impress your tech department and migrate to Linux.
Microsoft offers some tips on upgrading and transferring data, all while trying to sell you Windows 8.1.
The Independent has a mini-guide for those sticking with XP, and noted that Google plans to support browser Chrome on XP until 2015. Mozilla apparently hasn't announced an end-of-support date for Firefox on XP.