How to Make a Bootable USB Disk for Windows 8, Windows 7, Windows XP

1. Download the Windows USB/DVD tool from here and run it.
2. Click Browse and select the downloaded Windows 7 ISO file.
3. Click Next.
4. The next page asks whether you want to save this file to a USB or a DVD. Click USB device.
5. Connect a pen drive with at least 4GB space to your computer. Make sure you back up all data on the pen drive to your computer as it will be erased during this process.
6. Select your pen drive from the drop down menu and click Begin copying.
7. When this process is complete, you'll have a bootable Windows 7 USB ready.

Windows 8

1. Download the Windows Installation Media Creation Tool from here and run it.
2. Select the Language from the first drop-down menu.
3. Then select the Edition of Windows you want to install. Your choices are: Windows 8.1, Windows 8.1 N, Windows 8.1 Pro, Windows 8.1 Pro N and Windows 8.1 Single Language.
4. In the third drop-down menu next to Architecture choose whether you want a 32-bit or 64-bit version of the OS. If you need to see which version you're running right now, right click on My Computer and select Properties. There, you'll see the information you need under Windows Edition and System type respectively. Alternatively, check Microsoft's website for detailed instructions.
5. Click Next.
6. Plug in a USB drive to your computer. Make sure that it has at least 4GB space. If there's any important data on the drive, create a backup as this process will erase the pen drive completely.
7. Now you'll be asked to choose where to save the ISO file. Choose USB flash drive.
8. Click Next.
9. You'll see a list of USB drives connected to your computer. Select your pen drive from the list and click Next.
10. Now the Media Creation Tool will begin downloading the ISO straight to your pen drive. When the download completes, click Finish.

Windows XP

1. Go to the Windows XP SP3 ISO download page.
2. Select the language from the drop-down menu and click the big red Download button.
3. Download a free programme such as ISOtoUSB to burn the image to a pen drive. There are a lot of apps that let you do this and you can use any of these. We found ISOtoUSB easy to use and light, so we picked it over others.
4. Install ISOtoUSB on your computer and open it.
5. Click Browse and select the downloaded Windows XP ISO file.
6. Plug in a pen drive with at least 1GB free space to your computer. All data on this pen drive will be erased so make sure you have a backup.
7. In ISOtoUSB, select the pen drive from the drop-down menu.
8. Click the checkbox next to Bootable
9. Click Burn.

When the process is complete, a bootable Windows XP USB drive will be ready.