A quick search in my Documents and Settings folder and I think I've found something that will work. First off, I'm opening these in Wordpad, but they're listed as SQL files with tables and such, so if you have a spreadsheet reader you may want to try opening these files with that instead. Here's the first bit of text from the file as an example:
Anyway, it's going to be kind of a chore to find your exact sms file, you're going to have to open each file and look for the line above, that's why I used wordpad.
You can find these files in this folder:
C:\Documents and Settings\Administrator\Application Data\Apple Computer\MobileSync\Backup\d02f07f566cb03cdacfdce5 fccbe9d562c7a5295
That big long d02f0... yours may be different, but there should only be one folder to open anyway. Once inside that long named folder, start opening the files named like:
Go for the larger sized ones first, they've obviously got the most information, aka text messages.