After 8th April, 2014 Microsoft will be ceasing support for Windows XP.
The software will continue to work on PCs (after all, they can’t electronically yank it off your computers – well, not yet, anyway) but importantly there will be no more security updates. So consider your XP computers unprotected from viruses, worms, trojans and other malware after this date.
If you’re still running XP, realise that you are running out of time. Migrate to a newer, supported OS as soon as you feasibly can.