We are not allowed to link to downloads as it enourages piracy.
It's best to borrow one from a friend, copy the DVD, or if another version extract the ISO using ImgBurn, remove ei.cfg file using this tool
to burn an all-versions DVD to reinstall with your Product Key.
Or you can download one from the web - just be sure to rightclick scan with your AV, and test the HASH
to compare to official HASH
to make sure nothing has been added or deleted from Windows 7.