boot camp was lost

[aml]

Hey,I had been using boot camp to run Windows Vista for the past year without problem,but now when I go System Preferences-Startup Disk and I can start up only with Mac OS HD,boot camp was lost.
What's happened?
How I can back windows and not to lose files? Please help...
Thank you!

 

[Satcomer]

Does the Windows partition disk mount on your OS X desktop?

 

[aml]

No, it's not there.