Windows 7: Files won't open once associated with Excel

I have a friend who has Windows 7 and Office 2007. He needs to open tab-delimited files that are saved in the .dat format. He's wants to open them in Excel 2007.

We set up Excel as the default program (we had to manually browse to excel.exe. I also tried excelconv.exe). However, double-clicking on the file doesn't open it. It sorta blinks and then nothing happens.

We can open the files if we start in Excel and browse to the desired file that way.

Is there perhaps a problem with the conversion dialog not opening when you double-click something? I think this used to work on his XP machine with Office 2003.

From what I read here .dat isn't an Excel supported file.

Microsoft Office Binary (doc, xls, ppt) File Formats

I would think if that was the problem, the files wouldn't open when you opened them while already in Excel, but that's working (with the standard delimited file translation dialog).

These are just delimited text files, there's nothing hinky about the files.

In 2010 it doesn't seem to be a data import format either. I'm sure it was at one time. If they are fixed format text files you may be able to import them by renaming to .txt

Update: You don't even need to rename them. Just select all file types in the text import wizard and you can chose between fixed format and delimited.

There are two ways to import data from a text file by using Microsoft Office Excel:
You can open the text file in Excel, or you can import the text file as an external data range.

Detailed instructions contained in the following Article - Import or export text files - Excel - Microsoft Office

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I took a look at that. Both methods refer to having Excel already open and getting to the data in some way. But I'm sure we can all agree that one should be able to just double-click on a file and have it open in the appropriate program. It used to do so.

This seems like an odd combination of a Windows 7 problem and and Excel 2007 problem, because I would imagine Windows 7 controls the functionality of "you just double-clicked on the file; I know I'm supposed to open that file type in X application, so I'm going to open that application and then try to open the file inside it", whereas Excel then takes over the process of opening the file from there. I'm not sure at what point in that process the problem is occurring.

That's interesting. I just tried associating a .dat file with Excel 2010 and it opened it straight into Excel. This was just a random text file I renamed and it seems to have made a reasonable job of splitting it into columns. It wouldn't open with the converter and interestingly the converter in the open with dialog calls itself Excel. I wonder if you are picking that up as the default.

I'll check and make sure we're trying to use excel, not the excelcnv. I know I tried that first and it didn't work, which is why I then tried the excelcnv.

This machine had some sequence of events like 2007 installed, then uninstalled and 2003 installed with the 2007 converter, and then that upgraded back to 2007, something like that. I fear that's what's causing the problem, but I don't know how to fix it barring a full reformat.

Perhaps a valid question might be - what's the best way to completely and utterly delete all traces of Excel from a machine, returning all files and settings to their non-Excel state, so that I can then re-install and be sure that nothing will conflict?

That way hopefully whatever is causing the problem will be gone.

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