As of April 2014 Microsoft is officially finished supporting Windows XP.
Why it's important for you to upgrade now
If you are still using XP, or know of people who are it's time to upgrade them (and yourself)!
Microsoft will no longer be supplying updates and security patches. Those who create infections have been stockpiling XP vulnerabilities for months because if they wait for MS to drop support then they can use them forever, versus infecting machines now with these tricks and Microsoft patching XP to prevent those tricks from working in the future.
Also XP was released in 2001, and has well run it's course, now with 3 consumer operating systems from Microsoft having been released.
New hardware won't support XP, and neither will new software (Office 2013 for example won't run on XP or Vista). When Microsoft stops supporting XP, it will be a very short time before everyone else stops as well.
What if I use "X" software to protect me from infections
There are a lot of good protection softwares out there. One of the most popular amongst this community is Microsoft Security Essentials, which will also cease working on April 1st, 2014 (for XP machines).
Even if you have great protection software, it's still something that is added on TOP of your operating system, and if there are holes in your OS, infections will still be able to get in. 3rd party companies aren't going to be able to patch all the security issues in XP, and they'll only support XP for as long as there is a market. And it should be noted that XP's market share has been dropping fast and will continue to do so. Don't be one of the stragglers still hanging on past April 1st.
Where to go
Windows Vista, 7, 8, Linux, etc. are all available as upgrade paths. I personally would recommend Windows 7, as it has a good upgrade path from XP and currently has the largest market share of any Operating System. Meaning, much like XP, it will likely have a very long line of support. I figure if you stuck with XP for this long, you'll probably want something you can also stick with for as long as you can.
Other options exist and if you're interested you can discuss them in the comments below. I'll keep some links here for quick access
How to back up data:
When upgrading to a new Operating System, it's always best to do a fresh install, so any little bugs don't carry over. This means everything will be wiped clean, so you should back up all the data on your computer that you want to keep. Even if you do an OS Upgrade, there's still a chance your data could be lost (about 1 in 10 from the hundreds I've done for regular household computers). And you should be backing up your data regularly anyways.
The easiest route will likely be to get an external hard drive, copy everything you want to keep over to it, and then unplug the external drive before wiping your computer and installing the new OS.
For more information on data backup see our wiki page:
Compatibility and the difference between 32-Bit and 64-Bit
If you use older software, it may not be compatible with newer operating systems. This is always the case. Fortunately the vast majority of software that worked on XP will also work on Vista/7/8. So you shouldn't have much to worry about, but if you have any truly ancient software, now is the time to find a replacement.
Something many people are confused about when transitioning from XP to a newer operating system is the difference between 32 and 64-bit. So I'm going to clear it up so you'll understand what is best for you.
32-Bit: This is what computers used for the longest time. Back in the 80's when computers were considered powerful if they had 4 MB of RAM (roughly the size of one MP3), they started using 32-Bit systems. They knew that it would work great for a long time, because it had a max of 4 GB (or 4,096 MB). And it did last for a long time. But we got to a point where we were producing 4GB sticks of RAM relatively cheap and needed to change to something that could see all of the RAM and be able to use it.
64-Bit: This is what we gradually transitioned to from around 2004 to now. It can see below 4GB, just like 32-bit, and above to virtually any RAM amount that will exist in your lifetime (17,592,186,044,416 MB). To put that number in perspective, if each one of those MBs was equal to one second, then that would be roughly 35,000 years. 35,000 years ago was when neanderthals went extinct. So, it's a pretty big number. Which is why we're switching all our computers over to it. The only downside is that since it is so different, some programs won't work with it that would work on a 32-bit machine. Again, these are mostly programs from the 1990's, and before, but some newer ones may have issues too. But since we've been doing this 64-Bit thing for about a decade now, you're not as likely to run in to too many issues. So unless you absolutely have to use a program made for Windows 95, and refuse to find a replacement, you should go with 64-Bit to take advantage of having access to more RAM.
If you have questions regarding upgrading from XP to another OS that still has support, ask them below. This post will be pinned so the community will be here to help those making the switch.
TLDR: XP is getting dropped by Microsoft meaning infections will run rampant on it. Back up your data and upgrade to Windows 7, or something else with long term support. Ask for help with the switch in the comments below.