Windows XP will continue to run and your computer will continue to perform as it does at the present time. The world will not come to an end for those that have XP computers on April 8, despite all of the scare tactics to drum up new sales. It is really only businesses that have to worry about it and the possible security issues that may develop.
Yes what jd said. I am a software developer. I still believe that XP was one of MS's best. If your computer is still running it, why change until the computer dies?
If you are not a computer geek, I probably would not mess with Linux. Open source is a great concept, but not always a great practice.
When you do replace your computer and if you decide to go with a Windows system, Microsoft has a history of every other OS being a lemon and the next one being a nice system.
XP was a great system. The follower Vista not so much. They tried to do too much in too short of a time frame and got it wrong. The next one Windows 7 fixed the issues and was what Vista was trying to be. Then out comes Windows 8 again Microsoft trying be too much to too many and came out half baked. I am sure that Windows 9, if that is what it is called will be the next great OS.
My mothers computer recently died. She does not do enough to warrant the kind of computer that I would need. We simply got her a refurbished computer through Wal-Mart online. It cost $200 without the monitor. It came with Windows 7 Pro. A big plus. I did not want to deal with Windows 8.
For myself, I will probably wait for Windows 9 service pack 1. Even the cleaned up OS, they do not get the first release quite right. Those little issues are usually taken care of in the first service pack.
By the way I have a Microsoft subscription (the company I work for, paid for it as a perk) so I can download and use what I want. I run xp on my old computers that the kids use and the newer ones use Windows 7. The latest is not necessarily the greatest. Use what works the best for you.
An old computer can be helped if you clean it up, remove software that you do not use. Defrag it. There is a product you can download for free called ccleaner. The name actually stands for "Crap" cleaner. But they decided to clean up the name as well.