MS Office 2010 x64 trouble with .xlsx files

I've exhausted every measure and I cannot figure this out. One of the computers at my work is running Windows 7 x64 and I've installed Microsoft Office 2010 x64. Everything was fine at first, everything ran the way it was supposed to. Then I get a call from an employee saying that when he double-clicks an .xlsx file he gets an error. So therein lies the problem.

The ERROR: "...<filename>.xlsx is not a valid Win32 application."

Before I continue, the reason I am deeming this a Windows 7 issue and therefore posting it here is because when I log onto my profile on the same PC I can open .xlsx files perfectly fine. So something on his profile is broken. This computer is on a domain and both of our profiles are network logins.

What I've tried:

1. I've tried right-clicking the file and changing the default program used to open said file. The issue here is his profile doesn't recognize Excel as being a valid application. In other words, when I navigate to the directory to select EXCEL.EXE, I click it, and when it shows up on the programs list it catagorizes it as "Microsoft Office Component", and not Excel, as if to say it doesn't know what this is. However, I can opel .xlsx filed through the Excel program just fine. It may also be worth noting that when I first approached the workstation Excel was not listed in the Start > Programs > Office directory.

2. I've done a repair using the office files. After I went through the process I found that the programs were back in their spots in the Start > Programs > Office directory. But I still get the error when I double-click the file.

3. I've tried uninstalling office entirely and reinstalling the program. I still got the error.

4. I went under advanced settings within Excel and unchecked "Ignore other applications that use Dynamic Data Exchange (DDE)" and that didn't work either. Actually, it was already unchecked (checking it didn't work).

5. I've checked the registry and everything seems to be fine.

6. I've changed the settings under compatibility mode and to every option available and then no option (which is what's working on the other profile) and it still doesn't work.

There are not multiple variants of Office on this PC.

Suffice it to say adding another profile would be a painful process given the current situation. I need to fix it on his profile ASAP.

PLEASE HELP!