You have grub as your boot loader, the second stage of the boot process would read configuration from the second drive which told your computer how to boot both Linux and Windows. Now grub is complaining it can't find the Linux boot partition. You need to boot into a Windows recovery disc, you can create them from any Windows computer and fix your boot process.
Fix the MBR – Guide for Windows XP, Vista, 7, 8, 8.1, 10