I've installed Linux into my flashdrive from another flash drive while windows 7 is running. When I start up my computer with the flash drive in which linux installed , it appears 4 options ( Linux, Linux recovery, window , windows recovery ).Linux used to work smoothly but something happened and I could not open linux again. Terminal screen appears but it says there is a problem with system file . But I still get 4 options in start-up and I can open windows 7 if I connect the flash drive.But the problem is I cannot run Windows without connecting the flash drive in which linux was installed.When I disconnect the flash drive and start up the computer in a usual way, windows logo never appears and black screen appears and it says like  welcome to grub..there is no such a device..recovery mode..So how can I run windows directly like in the past? I worry if I lose the flash drive I will not able to run windows either.
I cannot run Windows without connecting the flash drive in which linux was installed
dual boot