Not too sure if you came across the need to keep both MS Office 2010 and 2007 or not. If you do and stuck with the same problem as me.. here is the solution.
First installed Office 2010 in a separate folder.
Choose to keep the old setup.
Proceed the installation.
After the activation and etc done.
You will most likely came across the same problem i did. Every time that you switch back and forth on both version, MS Office will try to reconfigure the software and you will loose your many valuable minutes of your life.
Here is the quick fix:
reg add HKCU\Software\Microsoft\Office\12.0\Word\Options /v NoReReg /t REG_DWORD /d 1
reg add HKCU\Software\Microsoft\Office\14.0\Word\Options /v NoReReg /t REG_DWORD /d 1
Run both command in command line to add two registry to prevent the reconfiguration.
Note: This registry fix is based on previous issue that happened with Office 2003 and Office 2007.
If you happened to have Office 2003 as well. You will need the below command as well.
reg add HKCU\Software\Microsoft\Office\11.0\Word\Options /v NoReReg /t REG_DWORD /d 1