Boot Linux from External Hard drive

Hi All,
I am new to CAELinux. I am using office computer for learning CFD which has Windows 7.0.

I had burned the CAELinux 2011DVD. Installed CAELinux on external USB HDD.

But now every time the computer starts I have to boot it through the CAELinux 2011DVD else it would start windows.I have also noticed that when I am running any program in CAElinux it starts the DVD.I also not able to save anything or anywork.

I had done the boot loader into the external HDD while installing first time through the DVD.

Can anyone help on this.
I have tried looking into the forum.But no luck so far.

While the PC boots you may get an option for a "Boot device menu" or similar if you press a certain key. On my PC I press [F12]. Then a list appears with different devices to boot from. Choose your USB device. You have to do this every time you want to boot the CAELinux HD.
If no such boot device selection appears, you can enter the BIOS setup and in a BOOT device sub menu you can set the sequence of boot devices. Increase the priority of the USB device above the internal harddisk (probably SATA device). This you only have to do once. If a bootable USB device is present this will be preferred over the internal HD.