I want to upgrade my Processor and Motherboard but I want to keep the OS setup(dual boot for Ubuntu and Windows7) intact.
Is it possible? What are the problems faced, if any?
Ubuntu will be just fine. The kernel will auto detect and handle everything. Windows on the other hand needs some help to deal with major changes.
With administrative privileges you should use sysprep.
c:\windows\system32\sysprep\sysprep /oobe /generalize
Put the above in a batch file right click on it and run as Administrator. Do this just before you shut your existing system down for the last time before the actual upgrade.
After the upgrade,on first boot, windows will re-detect all of your hardware.