You will have less disk space available for OSes.
No. It is entirely possible to install and run Ubuntu on a computer without ever having run Windows on it.
Ubuntu is safe. The majority of viruses and other malware on the internet are written for windows, so they wouldn't affect an Ubuntu computer. However, ubuntu is less user friendly than windows, so I would be careful and make sure you have a good backup for your windows computer.
you computer will be slower than before you install ubuntu....
There are no real risks. That is the beauty of virtual machines.
Ubuntu generally creates a different partition on your hard drive, formatted with the EXT4 filesystem. Therefore, without special software, you cannot access your files on Ubuntu from Windows. However, you can access your Windows files from Ubuntu without any trouble. When Ubuntu is installed, you get to choose whether to boot into Ubuntu or Windows when the computer turns on. That means that you cannot be actively logged into both Windows and Ubuntu on the same computer. However, you can install Ubuntu on a virtual machine, making the computer run Ubuntu inside an emulator in Windows. This makes it possible to run Ubuntu while you are logged into Windows. I do not recommend it, though. Ubuntu users and Windows users are in different operating systems, so you cannot just switch between them like you can in Windows accounts.
Any version of Windows and Ubuntu is no problem. I'm unaware of all the issues that might surround a Windows 7 / Vista dual-boot, but adding Ubuntu into the mix shouldn't cause any problems, provided the two versions of Windows are cooperating.
Yes, just format your Hard Drive and install a fresh copy of Windows.
Ubuntu is a whole operating system, not a simple program. It does not run on top of Windows, but instead of it. Thus user accounts on Vista do not come into play. Ubuntu supports its own user accounts, so once it is installed, no one except the person who installed it can use it unless an account is created for them.
Yes Linux can be installed on the same computer.
the operating system ie windows 7, ubuntu
Yes, it can be done from the windows installation disk, but it's cleaner if you remove ubuntu with the ubuntu live cd and then install windows.
A quick and relatively easy method of getting Ubuntu Linux - if you already have a Windows system and you want to run Ubuntu Linux on it - is to download Ubuntu and install it by using the Wubi (the Windows-based Ubuntu Installer) from this Ubuntu web site: http://wubi-installer.org You can use the Wubi (Windows-based Ubuntu Installer) to download and install Ubuntu Linux in Windows and this is very similar to installing any software program in Windows. One of the great benefits of using the "Wubi Installer" is that you can also uninstall Ubuntu Linux from Windows if you need to (in the same way as you uninstall any Windows program). When you use the "Wubi Installer", you DON'T have to do the following steps (that you would "typically" need to do) to install the Desktop version of Ubuntu Linux on an existing Windows system: download a Linux ISO file burn the Linux ISO file to a Linux CD set up your computer to boot from CD boot with the Linux CD to run Linux "Live" and get to the GNOME desktop double-click on the "Install" icon to start the installation routine run the Ubuntu Linux installation routine Ubuntu Linux Training Tips: The Wubi Installer is only used to install the Desktop (not Server) Edition of Ubuntu Linux on an existing Windows system - and not on a new or used computer system that doesn't have Windows already installed on it. All of the "download, burn, setup, and so on" steps listed above will be described shortly in upcoming sections. The Ubuntu Linux installation steps described above are required to install the Desktop and Server Editions (versions) of Ubuntu Linux - either on a computer system that has Windows (to create a Dual-Boot Windows / Linux system) or one that doesn't have Windows Ubuntu Linux Training Tips: Keep in mind that prior to installing Ubuntu Linux (or any Linux distro) on an existing Windows system, you need to do a complete backup of your Windows system - twice! Also make sure that you can use the backups that you have created to restore your Windows system from backup. (copied from "http://www.ubuntulinuxbookblog.com/wubi-installer-windows-based-ubuntu-installer-training-download-install-ubuntu-linux-in-windows.html" ) A quick and relatively easy method of getting Ubuntu Linux - if you already have a Windows system and you want to run Ubuntu Linux on it - is to download Ubuntu and install it by using the Wubi (the Windows-based Ubuntu Installer) from this Ubuntu web site: http://wubi-installer.org You can use the Wubi (Windows-based Ubuntu Installer) to download and install Ubuntu Linux in Windows and this is very similar to installing any software program in Windows. One of the great benefits of using the "Wubi Installer" is that you can also uninstall Ubuntu Linux from Windows if you need to (in the same way as you uninstall any Windows program). When you use the "Wubi Installer", you DON'T have to do the following steps (that you would "typically" need to do) to install the Desktop version of Ubuntu Linux on an existing Windows system: download a Linux ISO file burn the Linux ISO file to a Linux CD set up your computer to boot from CD boot with the Linux CD to run Linux "Live" and get to the GNOME desktop double-click on the "Install" icon to start the installation routine run the Ubuntu Linux installation routine Ubuntu Linux Training Tips: The Wubi Installer is only used to install the Desktop (not Server) Edition of Ubuntu Linux on an existing Windows system - and not on a new or used computer system that doesn't have Windows already installed on it. All of the "download, burn, setup, and so on" steps listed above will be described shortly in upcoming sections. The Ubuntu Linux installation steps described above are required to install the Desktop and Server Editions (versions) of Ubuntu Linux - either on a computer system that has Windows (to create a Dual-Boot Windows / Linux system) or one that doesn't have Windows Ubuntu Linux Training Tips: Keep in mind that prior to installing Ubuntu Linux (or any Linux distro) on an existing Windows system, you need to do a complete backup of your Windows system - twice! Also make sure that you can use the backups that you have created to restore your Windows system from backup. (copied from "http://www.ubuntulinuxbookblog.com/wubi-installer-windows-based-ubuntu-installer-training-download-install-ubuntu-linux-in-windows.html" )