GNU, Knoppix

[Stefan Walraven]

Hello,
A few weeks ago I installed for the first time Linux (Ubuntu).
I have Windows on my computer, too, becaus I'm still learning with linux.
I have also "Home Cinema Linux", a program to see movies etc without really 
starting my laptop. But after installing Ubuntu, that home cinema linux didn't 
work any more. So yesterday I installed it again, but now, when I start my 
computer, windows immediately starts. I can't choose between ubuntu or 
windows. Linux is still on my hdd, but I can't start it any more. 
A friend told me that I can solve it with knoppix and I have to reinstall the 
GNU, but he doesn't know exactly how. 
I hope some of you can help me.
Thanks!

Greetz,
Stefan