Let's get the bad news out of the way first. Windows XP isn't eligible for the free update to Windows 10. That means you will have to buy a licence.
The second piece of bad news is that you'll have to do a clean installation of Windows 10, as there's no way to upgrade and keep your files, settings and programs. It isn't a limitation of Windows 10 but of XP: even if you wanted to upgrade to Windows 7 from XP you'd have to wipe your hard disk and start again.
See also: Windows 10 release date and features
How much will it cost to upgrade to Windows 10 from XP?
For versions older than Windows 7, or non-genuine versions, you'll have to buy Windows 10 Home or Windows 10 Professional. Windows 10 Home costs £99 from Microsoft and Professional will set you back £189. You can choose a download or a USB.
You can read our hands-on review of Windows 10 here, but the bottom line is that it is certainly the best version of Windows yet.
Here's how to find out if Windows 10 will work on your PC. The minimum requirements aren't too demanding so even an older PC or laptop with a meagre specification should be able to run Windows 10.
Should I upgrade from Windows XP to Windows 10?
As we often say, you'd be surprised at how much your computer appears to speed up when you install Windows afresh. Starting from a clean hard disk means there's no build-up of programs that start with Windows, slowing it down and using up precious memory.
Another great upgrade is an SSD. Solid-state drives are much, much faster than traditional hard disks and can give a new lease of life to a PC you thought was destined for the scrap heap. Here's how to install an SSD (or upgrade your laptop to an SSD).
If you have a machine that's over seven years old, it may be a better idea to save the money on a Windows 10 licence (and an SSD) and put the cash towards a new laptop or PC.
Whether you upgrade from XP or buy a new PC that's already running Windows 10, there are plenty of reasons why you should - not least that XP is now very old. And if you didn't think it was that old, check out the video below of teens experiencing Windows XP for the first time.
How can I update XP to Windows 10?
If you decide it is worth splashing out for Windows 10 Home or Pro, you'll have the option of a physical disc or a digital download.
It's unclear whether you will be able to run the downloaded version from within XP but even if this is an option, it will erase everything on your PC's hard drive before installing Windows 10.
So, before you begin the upgrade you will need to copy everything you want to keep to an external hard drive, USB thumb drive or a cloud storage service such as Dropbox or OneDrive.
Also, find your software installation discs and licence keys. If you have misplaced the keys, use a free program such as Magical Jellybean Keyfinder to search the Windows registry for these codes, and then write them down.
If you keep your email inbox or any archives, be sure to back these up as well, and export internet bookmarks and other settings that you want to keep.
Then and only then can you begin the actual installation of Windows 10. There's no guarantee that all your programs will be compatible with the new version of Windows, nor your old peripherals - specifically printers and scanners - so it's worth checking online to see if there's any information about their compatibility with Windows 10. If a Windows 7 driver exists for your particular model, it should work in Windows 10.
How to upgrade to Windows 10 from XP or Vista for free
Microsoft has said in a blog post that everyone testing Windows 10 on the Insider program will get to keep on using Windows 10 after the 29 July launch date since the program isn't stopping. This means you can sign up to be an Insider before 29 July, install the preview and get upgraded to the final version (and subsequent preview versions) without paying a penny.
This will be good news for some, but bear in mind that you'll be using what is essentially beta software again when the next preview build is installed after the launch version of Windows 10.