I had both Windows and MacOs X on my mac book and both were working efficiently.
Suddenly it will never start on windows. I start my computer, keep the cmd button held but it will always start on mac os x.
The only thing that i can recall that changed on my computer since the last time i loged on Windows normally, is that i added RAM memory on the laptop. I actually removed the 2X1GB modules and replaced them with 2X2GB modules.