Thanks for replying on my question.
I created a bootable pendrive of windows seven from windows seven iso file using a software. Now windows 7 is installed successfully on the laptop for which I created bootable pendrive but I lost the iso file. Now I have only this working bootable pen drive of windows 7 but I can not keep the files this way. I need to use the pendrive for other purpose too.
I tried to create iso from the files of the pendrive on my ubuntu using command
mkisofs -o windows7.iso bootable-pendrive-path
It creates an iso file but when I try to create a virtual machine in vmplayer, it shows error "operating system not found"
I was not getting this error using my old iso file.
How can I create working iso file so I will be able to boot win7 in KVM, VMplayer or virtualbox.