Is there any software that can play a subtitle file without a video file?
You might consider installing a subtitle editor like Aegisub. I use Aegisub to sometimes make subtitles, and sometimes use it to preview subtitles without video. I've never watched an entire movie's worth of subtitles this way, so it may not be the most comfortable option, but you might look into it.
To play subtitles without video in Aegisub, you can use these steps.
Open the SRT file in Aegisub. (If you let Aegisub associate with SRT files, you can just double-click on the SRT file in Explorer.)
In Aegisub, select Video → Use Dummy Video. Enter a video size in pixels and select a background color. You have to enter a duration in frames, but it shows you the result in hours:minutes:seconds, so you can fiddle with the number of frames until you see the time is equal or greater than the length of the video you'll be watching.
Select Subtitles → Styles Manager. Under Current Script, highlight "Default" and click Edit.
The Style Editor box will appear. You can modify the font face, font size, margins, and alignment.
If you position the laptop underneath your view of the TV, you might want align the subtitles to the top of the laptop screen (alignment 8) so you don't have to glance too far from the TV to read the subtitles.
If you find a set of style options you like, you might use the Styles Manager "Storage" options to save them for later use.
Select Video → Detach Video, then maximize the new video window. There will still be some tool bars on the edge of the video, but this will hide most of the editor functions. It will look something like this:
Mister, I have the perfect solution for it. http://download.cnet.com/Greenfish-Subtitle-Player/3000-13632_4-75748013.html This is like a tranparent kind of a bar with dark bold subtitles which you can arrange on your screen while the movie plays.
You could use movie-maker to make a blank video of longer then the longest movie you're going to watch, save it at the smallest possible compression size, and then use VLC to play both the blank video and the subtitles file of the movie you're watching (though you'll have to start the blank video within a couple of seconds of when you start the movie). You can then use VLC's options to increase the size of the subtitles.
Instructions for using external subtitle files with VLC can be found on the videolan how-to page