Since Microsoft will stop all support for XP on April 7th, they will no longer offer Microsoft Security Essentials for it. If you already have it, they may continue with updates to MSE for awhile, but that's not for sure.
Microsoft will no longer issue security patches for XP, so if you can't take if off-line, be sure you have the best security software you can on your computer. That won't help with the unpatched security holes in the operating system, but it might buy you some time.
Heading for the gardens!