Depends on just how fragmented it is. (The .txt extension is really weird for a texture file...stupid Verant.)
I assume you're using WinXP. Unfortunately most defraggers, including the one in XP, don't perform a really complete defrag, and they're slow about not doing it.

As long as the file isn't in a tremendous number of fragments, it shouldn't cause much of an issue for you. If it is in fact just all the textures in the game, then the data will be read in blocks as you change levels or whatever, maybe when a new player comes in, rather than needing lots of continuous access.
You can also download the trial version of PerfectDisk. It actually performs a complete defrag of every file, consolidates free space, and optimizes file placement. Even DiskKeeper won't do all that for some reason. PerfectDisk is also able to optimize the MFT, directories and swap file, which the XP defragger can't, but most others do. The trial version is completely functional, not crippleware.
Large files DO take a significantly long time even in PerfectDisk. I watched for several minutes as a several hundred MB file was defragged, you could be waiting a long time for that texture file to be done.
I suppose it's possible that the XP defragger isn't even capable of defragging quite such large files. Or it has simply determined that it is efficient enough even though it's fragmented. DiskKeeper (which XP's defrag is based on) also does that. It leaves lots of files fragmented but considers them optimal.