Where can I download IE8 for Windows 7

For starters, let me emphasize that this question is asked on a regular basis, and there are a few myths surrounding this scenario.  The simple answer is that there isn’t a stand-alone download for IE8 on Windows 7 (and unfortunately, the Vista version of IE8 will not work).  The only way to get IE8 back is to remove IE9 using one of the following methods:
Control Panel -> Programs and Features -> View Installed Updates (on the upper-left)
Scroll down until you find Windows Internet Explorer 9.  Highlight and click the Uninstall button.
As an alternate method, you can open up a command prompt with full admin rights… Start -> cmd -> Ctrl+Shift+Enter -> acknowledge the UAC prompt.  Within the elevated command prompt, paste in the following, run it and then reboot:
FORFILES /P %WINDIR%\servicing\Packages /M Microsoft-Windows-InternetExplorer-*9.*.mum /c “cmd /c echo Uninstalling package @fname && start /w pkgmgr /up:@fname /norestart”
In the event that method still doesn’t work, execute a System Restore to a point prior to when you installed IE9:
Windows 7 System Restore
If that doesn’t work and you have also installed Windows 7 Service Pack 1 already, you may need to weigh your options.  If you really don’t like IE9, you would potentially need to temporarily uninstall SP1, then uninstall IE9, ensure that IE8 is working, and then re-install SP1.
Finally, you would want to ensure that IE9 isn’t automatically installed again by Windows Update, so you should probably use the Internet Explorer 9 Blocker Toolkit:
Disable Automatic Delivery of Internet Explorer 9