Problem installing LMD with windows7

[zenofronia]

I have Windows7 on my HD. LMD is on DVD. I try to install LMD and instead Windows7 starts up. I've installed LMD with this disk on another machine which is the same model except without windows and it worked fine. My machine is IBM ThinkCentre with 80GB HD, dual core 3.5GHz. Plenty of space. Whasup?

Thanks, Zenofronia