So, you want Windows 7. You've read our guide to Microsoft's latest OS, you've worked out the benefits of making the switch are the right one's for you, in fact you may already have chosen which version you want to install and have your Windows 7 disk in your hands, the question now is how do you actually upgrade your computer to Windows 7? Well, that's why we're here.

Let's get the easy one out of the way quickly. You can't. Whether you've got a blank computer, Linux or you're still running Windows ME for some strange reason, then you'll have to buy the complete version and do a clean install. Back up all your personal files, put them on a DVD/USB stick/external HDD, do a clean install of Windows 7, make several cups of tea and then put your files back on again. Job done.

First of all, bear in mind, you XP users, that if you're planning on using the feature of Windows 7 that allows you to run a virtual version of XP then make sure you've got Windows 7 Professional Edition or Windows 7 Ultimate. The Home version does not have that function. It doesn't mean that you won't be able to run all your Windows XP supported programs but you may have an issue with the odd obscure one. Ok? Right.

Step 1: Buy
Go down the shops - virtual or otherwise - a pick up an upgrade version of Windows 7.

Step 2: Check you system
It's a touch on the anal side but for measures of completeness, download and run the Windows Upgrade Advisor software. It'll take a quick look at your machine and tell you if you're going to have any problems with the current software you're running if you intend to transfer it over to Windows 7. Chances are that if it does come up with any issues, they'll probably still run fine but it might be worth doing this process for piece of mind. You can then have a look online for the software developer's site and see if they have any advice on the matter.

Step 3: Back up
From XP you'll need to do a Custom install rather than a straight Upgrade. It'll wipe all the files on your system, so grab yourself an external HDD of some sort or a very large USB stick and prepare to move files. You can do it manually, but an easy way to do it is by downloading and running the free Windows Easy Transfer software. It'll create one massive file with all your docs, sheets, photos, music, vids etc which is great if you have the space for it. What it won't copy is your programs and installers, so you can either pick those up from the Internet once you've finished the upgrade or copy them over manually which is probably a bit unnecessary.

Do bear in mind here that Windows Easy Transfer will not work if you're planning on going from a 32-bit version of Windows to a 64-bit version. If you're doing that you'll need to back up your files by hand. Secondly, it won't copy your media licenses, so if you have DRM-ed music and videos, you'll have to pick them up elsewhere afterwards. Another reason why DRM can be a total pain in the recharge socket.

Step 4: Run your anti-virus

Again, marginally on the picky side but the last thing you want to do is carry your malware over if you're doing a fresh install, so have a last run of your anti-virus program for good luck and then switch if off.

Step 5: The big install

Ok, let's do this. Connect to the Internet so that the program can pick up any new updates as it goes. Disk in, run the program and select Custom install. Choose the partition that currently has XP on it - usually C: - and hit install.

Step 6: Make tea

Step 7: Replace your files

Run Easy Transfer again which will plop all your personal files back in the equivalent places on your spanking new OS. If you haven't used this program, then you'll have to do it by hand. Make sure you do this before adding the applications back in, so that your programs will know where to look for the files or at least have a go at finding them if you copied them to the wrong place.

Step 8: Update your drivers
Run Windows Update to make sure you're all patched and that you've got all the relevant drivers to keep your system happy.

Step 9: Clean up
A couple of weeks after the install, run Disk Clean, hunt down your previous windows install if it's indeed still there and delete it to remove any last traces of what is now totally redundant. That'll reclaim all those sectors for good. You can even defrag if you fancy it too.

Step 10: Enjoy your new OS.

Sadly this isn't quite as straight forward as it looks. If you're planning on going from a 32-bit version of Windows to a 64-bit version then you'll have to a do a Custom install even though you have an Upgrade version of the Windows 7 software. Go to the "Upgrading from Windows XP" section above and follow the steps. Also, if you're planning on moving from a Home or Ultimate version of Vista to a Professional version of Windows 7; if you're trying to go from a Business Vista to an Ultimate or Home version of 7, or in fact if you'd like to go from Vista Ultimate to any non-Ultimate version of Windows 7, then again, you'll need to do a Custom install, so you'll have to follow the XP steps above.

Step 1: Buy Windows 7 Upgrade
Go down to the shops or online and buy yourself the relevant edition of the Windows 7 Upgrade that you wish to install. You can go from any edition of Windows Vista to any edition of Windows 7 but do bear in mind that if you're crossing from one type to another, you'll probably have to do a Custom install as mentioned and laid out above rather than a straight Upgrade.

Step 2: Install Windows 7
The advantage of doing the Upgrade option is that you don't need to muck around with saving any files or anything like that at all. Just put in the disk, hit the Upgrade option and it'll keep all your settings just the way they are. The only thing you will want to note is if you use a finger print reader, then make sure you've got a copy of the system password before you install as it won't remember your finger print patterns.

Step 3: Make tea

Step 4: Update your drivers
Run Windows Update to make sure you're all patched and that you've got all the relevant drivers to keep your system happy.

Step 5:  Enjoy your new OS

For one reason or another, Microsoft didn't want people using beta and RC versions of Windows 7 to be able to use the simpler Upgrade option. You can still buy the Windows 7 upgrade software, but you'll have to do a Custom install option as in the Windows XP example at the top. However, if you'd like to, there's a little hack-aroo to get around that nonsense. It goes a little something like this...

Step 1: But Windows 7 Ultimate upgrade
All RC versions of Windows 7 are Windows 7 Ultimate, so this is the version you'll have to buy if you intend on using the hack.

Step 2: Find the file
Insert you Windows disk into your machine and copy all the files to your computer rather than actually running the install. If you have no disk drive and you're using an ISO image, then use the Windows 7 extractor to get hold of the files. Once extracted go to the sources folder and find the cversion.ini file. Open it up and change the MinClient line value of 7233.0 to 7100. Save it. Close it and run the setup.exe file from the same folder and run the installer as normal.

Step 3: Install Windows 7
Select the Upgrade option as the wizard starts, make tea and enjoy your new OS.