You may refer to this tutorial even if your BIOS won’t let you boot from USB.
1. Live CD
To install Ubuntu on a computer that currently runs Windows, you need to download the installation file and burn it onto the CD, which you can then use to install Ubuntu. Once you’ve downloaded the file, follow the instructions below to burn your CD, depending on which version of Windows you are currently using.
You can find tutorial here.
2. Live USB
To run Ubuntu from a USB stick, the first thing you need to do is insert a USB stick with at least 2GB of free space into your PC.
The easiest way to put Ubuntu onto your stick is to use the USB installer provided at pendrivelinux.com. You’ll need to download and install and follow the instructions.
Download Pen Drive Linux's USB Installer
Once the Windows installer has been downloaded, you need to open it to install Ubuntu. You’ll find detailed instructions below. If you need further help, support options are listed at the bottom of this page.