After a having new Windows installed to my computer, the Office Home and Student 2007 which I had installed disappeared and was replaced by a trial edition. I have not activated it. Do I uninstall it and run my disk again? I want it back permanently
Sounds like, yes, you will need to do a little bit of work to get your fully functional version of Office working once again. Since you have the disc and product key, this shouldn't be a problem.
Upgrade the Trial Version or Remove and Reinstall?
Two different approaches to this problem exist: upgrade trial version and uninstall/reinstall. Some versions of the Office Trial version are upgradable to the full version which eliminates the need for uninstalling and reinstalling the software, so this is the first thing to try.
Note that you can only upgrade the trial version for the retail version that you have. For example, since you have Office Home and Student 2007, the trial version on your computer must be the trial version for the Office Home and Student 2007 software. If the trial version is for a different version of Office, then uninstall it and use your disc to install your software.
Assuming the trial version is the Office Home and Student 2007 version (as that's most likely), let's move on. Launch the trial version and see if the Activation Wizard appears. If so, click the option that says, "I do not want to activate my copy. Instead, I want to convert to the full version now." Click the Next button followed by Enter Product Key. From there, enter your 25-digit product key which should be affixed to the CD case of your Office 2007 disc. Click Continue and agree to the terms. Click Install. Now, your trial version is actually the fully functional version!
What if the Activation Wizard doesn't appear? That probably means that you've already activated the trial version so that you can start using Word, Excel, and the other programs. No problem, launch Word and then click the Office button. Click on Word Options and then on the Resources link in the left pane. Click Activate. From there, you'll enter the product key and convert the Office trial version into the fully functional version of Office 2007.
If the trial version is not upgradable, use Add and Remove Programs (Programs and Features in Vista) to remove it before installing the Office 2007 disc.