There's no need to write a C program to convert test to tabs. Word will do it much more quickly with find and replace.
If there is more than one space separating two columns, then you can replace 2 spaces with a tab, saving a step later.
When I have to do this kind of thing, with multiple spaces between columns, I usually replace 3 spaces with 2 until there's only 2 spaces left, then replace the 2 with a tab.
SD