1. System restore to Friday.
2. Repair install of Windows
3. Clean install of Windows.
I've never seen this happen with an official Microsoft supplied version. Did you already complain with them and asked your money back?
Kees
Last Saturday I downloaded Office 2010 and upgraded from Office Home & Student 2007. Everything seemed to work okay the rest of the day. On Sunday, I booted up and every program in my startup list opened in a Word 2010 window. Every desktop icon I clicked on also opened a Word 2010 window. I couldn't connect to the internet or run any programs. Every program opened with Word 2010. It appears that somehow Word 2010 took control over all my file associations.
I then logged on the internet with another PC and looked for solutions. In my quest to solve the problem, I manged to crash the PC and had to dig out a month old cloned back-up in order to get my PC active again. The clone still has Office 2000 on it, since it was made before I loaded Office 2007 and upgrade to Office 2010.
At this time, I am very reluctant to install the Office 2010 until I can get some help in figuring out what I need to do to avoid the takeover of my Desktop and programs by Office 2010.
As information, no other programs were installed to my PC on Saturday except for the Office 2010. I don't know if it matters, but I did not uninstall either of the previous Office programs.
I am running Windows XP Version 5.1 (Build 2600.xpsp3_gdr.10021601515: Service Pack 3) on an Emachine PC.
Thanks for all help and solutions.

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