If you use one of the most common terminal programs like Hyperterminal (on nearly all Windows OS's under Programs/Accessories), best thing to do is to set it in logging mode as follows:
Start Hypterminal
Click Transfer and select Capture Text
Specify a file name and disk location to store your output
Click Start
Issue the show tech command
When you've finished, click on Transfer and select Capture Text
Select Stop
All the other terminal emulators I've ever used do something similar to this. If you're using something other than Hyperterminal, just have a little poke around the program options and I'm sure you'll find it.