I need to get those windows files. Please let me know whether there is any procedure to get those windows files
When you overwrote Windows with Ubuntu, you also changed the file format. Luckily, you can recover files from an NTFS partition with a Ubuntu Live CD/USB. This page gives a rundown of how to do it.
if you have windows currently working then use easybcd. or if u have currrently ubuntu working then use grub2
https://help.ubuntu.com/community/Grub2 install and backup ur current boot to pendrive.
or else use livecd of windows to recover boot loader.
be carefull u face a hardware issue if u plug out power from it while working