“The install in progress conflicts with a previously installed Microsoft Office 2010 Server product”

SharePoint 2010 is fun. SharePoint 2010 is easy. I mean, for example, years back working with Windows operating system installation was a arduous task. Deep blue screen, white lettered alphabets, few instructions, shortcut keys to answer either YES, NO, CANCEL, PRESS ANY KEY TO CONTINUE, and the corrupt dll files all plagued us till Win2k3. And then came Vista with the easiest ungeeky method of installation, and same for Win2k8. In the SharePoint side of things, it started off as easy in WSS until MOSS 2007 came into the picture and it was all a picture of Hiroshima and Nagasaki all afresh. Now we breathe some air of relief with SharePoint 2010 configurations made easy in one simple Wizard screen. If we thought it was over, we were all probably not very right.

This is one of the reasons I believe that there will never really be a renegade robot or software that will take over the world, Sarah Connor can go about a normal life.

With SharePoint 2010, installing, uninstalling, reinstalling, re-uninstalling is just so tempting at the slightest thought of problem. But you will get bitten a few times. Language Packs is one. Office Web Access is another. These guys can ruin your 5 minutes eternal coffee time.
Here is one example, see the screenshot:

I just yanked off an installation because someone in the team downloaded a custom code, and installed it in my dev environment. This killed my Central Admin one time. Every other site was working except my CA. SharePoint 2010 is tempting. I figured rather than looking for the problem, yank it off and reinstall after a proper backup. So, I uninstalled. I began re-installing and just after the product key page I got this.

This particular problem is caused by Language Pack. I had installed a French language pack because half my users are French speaking. So you can imagine.

SOLUTION:
1. Stop the installation.
2. Go to Control Panel --> Programs and Features
3. Identify the language pack for SharePoint
4. Uninstall
5. Reboot

Now you can proceed to install your SharePoint.