Windows 7 - How to instal Windows 7 Professional over Windows 7 home premium?

When I bought a Dell desktop computer, it came with windows 7 home premium pre-installed. The computer runs super at the present time. In order to run Xp mode and remote computing, I purchased Windows 7 Professinal OEM. I wish to install it over Windows 7 Home Premium in order to avoid re-installing all software installed under Widnows 7 Home Premium. Please advise me how I can do that.

If you opt for "upgrade" instead of "custom(advanced)" in the step 6 of the tutorial Clean Install Windows 7, it should work .

Take a look at this:
Windows Anytime Upgrade - Upgrade your Windows 7 edition - Microsoft Windows

No install files needed.
Only the Upgrade key is need.
Anytime upgrade only adds-on the Programs & Features from version to version.
Windows Anytime Upgrade - How to

Is Windows 7 Pro considered as Upgrade? As described in the post, my DVD is OEM,not upgrade.

Yes, it's an Upgrade.
OEM/Retail makes no difference in htis instance

It took about 5 min to complete the update Windows 7 professional.
Thank you so much for your info.