The problem may, if you are using dual boot option to start Windows 8 and other earlier version of Windows. Once the installation of Windows 8 gets over, you wont be getting an option screen to choose which OS to boot. Windows 8 Starts By Default On a Dual Boot Installing 7989 as dual boot (issue).
It happened to me once with build 7955 and I used EasyBCD 2.1 to recreate the missing entry, but the "Repair" method is safer in my opinion.
If you have installed the latest leaked build (7989) on a separate partition (Dual Boot), of course the installation will go smooth without a hitch. Once the setup gets completed and all restarts had processed you will face a shiny new build of Windows 8
Here comes the issue...
1, After a manual restart you will find no boot option relating to choosing which OS to boot up, Windows 8 started instantly.
2, After running MSCONFIG you will notice that there was now only 1 option and that was for the current running Windows 8.
How to fix the issue...
Boot up using the Windows 7 DVD and choose the advanced options, at which the "searching for Windows" dialog appears. Seconds later you will be prompted that a Repair & Restart was needed. Click the "Repair & Restart" button. And you will be given the options you was first expecting.
- Windows 8
- Windows 7 (Recovered)
After selecting Windows 7 (restored) all will be fine to you. This may be an isolated case but for those who experience the same dual boot issue then follow the guideline above.