How to add text to specific animation frames
If you don't want to mess around with either of the free video editor versions available from Windows, WinXP (Windows Movie Maker) or Win7 (Windows Live Movie Maker) as these may not be flexible enough for your project, then you can try out a pro version with a free demo (good for 30 days) of Sony Vegas Pro 11.

Once you set up your trial version, add your video to the timeline, then use the "media generator/text" (title) features to add the titles you want. There are lots of options on the text generators.

Three links that are of interest.

Free Demo Version of Vegas Pro 11 (make sure you choose the correct version for your computer as in 32 vs. 64 bit):
http://www.sonycreativesoftware.com/download/trials/vegaspro?keycode=64506

Tutorial on how to use the media generator/text on Vegas Pro 11:

                
            

Expert advice and overview of Vegas Pro media generator:
http://www.sonycreativesoftware.com/media_generators_in_vegas_pro_software

Likely you can get your whole project done under the 30 day trial period and render a final version ready to post or show. If you don't understand how to render there are tons of tutorials out there, so just for fun I'll add one more link: