Vista won't boot. I don't have the installation disk with me, can I install Ubuntu to access my files even though vista won't boot?

I have managed to access my files with the demo but I'd like the full version. If I install Ubuntu while my vista OS isn't working will I lose my files?

I would boot to the live CD and back up the files from Vista onto a separate drive. Then do a full Ubuntu install and try to forget Vista ever existed.

When dynamically resizing partitions (especially shrinking), as usually happens when you install Ubuntu alongside Windows, there is always a small but significant risk of data loss. So if there are no backups, this is not a good way to access the data.

The same CD/DVD/USB that you boot from to install Ubuntu can first be used to access and back up any documents and other important files. Just select Try Ubuntu instead of Install Ubuntu. You'll get a working Ubuntu desktop which you can use to access files in the broken Windows system.

To back up your data files, don't put them on the live environment's desktop -- files written to the Ubuntu live CD/DVD/USB environment exist in memory only and disappear when the system shuts down or reboots. Instead, put them on an external drive (not the one you booted from), burn them to a CD/DVD, email them to yourself, transfer them over the network to another machine (Ubuntu supports networked file sharing with Windows machines), or use a cloud storage service like DropBox or Ubuntu One ... just make sure your files are somewhere safe.

Now that you've done that, unless you intend to attempt recovery or reinstallation of the broken Windows system, you can simply install Ubuntu and tell the installer to use the entire disk, overwriting the old Windows system.

You Try Ubuntu, you don't have to reboot to start the installation -- when you're done backing up your files, just run the Ubuntu installer by double-clicking the Install Ubuntu icon on the desktop.