Non-System Disk. Press Any Key To Reboot

I have an old Macbook Pro that dual boots OSX Lion and Windows 7.

Suddenly now if I try and boot Windows, I get this message: Non-System Disk. Press Any Key To Reboot

I can't actually insert my Windows 7 disk because my cd drive is broken and at the moment I don't have an external disk drive.

Is there any way of fixing this by maybe burning the Windows 7 CD to a USB or something like that?

Edit: Just remembered, I can actually access the Windows 7 files through the mac side and I think I can write to it... If Windows is having a problem booting could I try and add/edit/replace the necessary boot files to Windows?


Thanks for your time,
Zak