I dual booted my system with Linux Mint on a Windows 7 operating platform. I later thought it would be better to use Ubunta as I am a newbie to the system and there is more help available. I tried to uninstall Linux Mint through Windows but I am not sure I did. I then installed Ubunta from a CD and the whole system crashed. I am now unable to boot beyond the BIOS screen and am using Ubunta CD to access the internet. I would be grateful if you could shed any light on what has happened. Unfortunately I have no separate boot up disc.
Karen:

Hi Karen,
Using windows to uninstall Linux is not good. IF you have your install cd you can install form the ubuntu cd using the replace existing Linux distribution option.
In your Bios you should be able to either hit F9 to select a boot device or go to the systems options to boot from CD. then select install, and use the replace existing Linux option.
,Ron

When you installed Linuxmint it replaced boot loader.
When you removed Linuxmint you removed bootloader
Options are either repair windows bootloader or
Install Ubuntu and it will install it's bootloader enabling you to boot windows & ubuntu.

Open a terminal from live-cd since you're able to boot the cd and run command,