Windows XP

Microsoft states: After April 8, 2014, technical assistance for Windows XP will no longer be available, including automatic updates that help protect your PC.
While it's true that you can keep using your PC with Windows XP after support ends, we don't recommend it. For starters, it'll become five times more vulnerable to security risks and viruses, which means you could get hacked and have your personal information stolen..
Source: http://windows.microsoft.com/en-us/windows/end-support-help

If you are still using Windows XP, you should seriously consider upgrading your version of Windows or replace the computer with one that includes Windows 7, Windows 8.1, or Windows 10.
Windows 8 can be upgraded to Windows 8.1 for free.
Windows 7 and 8.x can be upgraded to Windows 10 for free until July 29, 2016.

See the Windows 8.x and Windows 10 sections of this site for more information, tips, etc.

How to determine your version of Windows and Service Pack level
Get the latest service pack or update for your version of Windows

• Windows 10
  • Due to be released summer 2015, replaces Windows 8.x (free upgrade for Windows 8.x and Windows 7 users)
• Windows 9 - never existed
• Windows 8.1
  • Released in October 2013, replaced Windows 8 (free upgrade for Windows 8 users)
  • System Requirements
  • Latest Service Pack: Update April 8, 2014 (KB 2919355)
• Windows 8
  • Released in October 2012, replaced Windows 7
  • System Requirements
  • Latest Service Pack: (free upgrade to Windows 8.1)
• Windows 7
  • Released in 2009, replaced Windows Vista
  • System Requirements (less than Windows Vista)
  • Latest Service Pack: Service Pack 1 (SP1)
  • Hotfix rollup for Windows 7 SP1 - contains 90 hotfixes released after Service Pack 1 (SP1)
• Windows Vista
  • Released in 2007, replaced Windows XP
  • System Requirements
  • Latest Service Pack: Service Pack 2 (SP2)
• Windows XP
  • Released in 2001, replaced Windows 2000 Professional and Windows ME
  • System Requirements
  • Latest Service Pack: Service Pack 3 (SP3)
  • Here are a few (of several) methods to view how much memory (RAM) and what speed processor(s) the computer has.
    • Click Start, then (Settings if you see it), then Control Panel. If you see Switch to Classic View on the left, click it. Double-click the System icon.
    • Click Start, then Run, then type dxdiag and hit Enter on the keyboard. In the System Information section, make note of the Processor and Memory.
    • Click Start, then All Programs (or Programs), then Accessories, then System Tools, then System Information. Make note of the Processor and Total Physical Memory.

Backup your data to removable media such as a USB memory stick, CD/DVD, or external hard drive.

• Copy the contents of My Documents and any relevant files/folders on your Desktop.
  NOTE: Outlook Express email and address book data is NOT contained in My Documents. Separate Outlook Express instructions are further below.
  1. Click Start, then All Programs (or Programs), then Accessories, then Windows Explorer (NOT Internet Explorer). If you don't see the Address field at the top, click View, then Toolbars, and make sure Address Bar is selected.
  2. In the Address field at the top of the window, type %HOMEPATH% and hit Enter on the keyboard.
  3. The contents of the following folders are generally the most significant:
     • Desktop (shortcuts can be ignored)
     • Favorites (these are the bookmarks within the Internet Explorer web browser)
     • My Documents (also contains Downloads, My Music, and My Pictures folders)
• If you use the Mozilla Firefox web browser, see the following:
  Restore bookmarks from backup or move them to another computer
• If you use the Google Chrome web browser, see the following:
  Import or export bookmarks
• If you use Windows Live Mail for email, see the following:
  Windows Live Mail - Backing up Your Data
• If you use Outlook Express for email, see the following:
  Outlook Express - Backing Up Your Data
• If you use Microsoft Outlook 2002, 2003, or 2007 to manage email, calendars, and/or contacts, see the following:
  How to manage .pst files in Microsoft Outlook. Note: We do not use Microsoft Exchange, so in relation to our email system, you can ignore references to it.
• If you use Mozilla Thunderbird for email, see the following:
  Moving Thunderbird Data to a New Computer
• Other software may store your data elsewhere. If you do not know where that data is stored, consult the software documentation or contact the software manufacturer.