UNIX for Dummies Questions & Answers

I run cygwin on windows 7, and have been using the windows command line. I've been trying to gunzip some previously compressed large sequence output files in .txt.gz format. This worked for about the first 10 files and then for the rest of them the file (as viewed using the 'head' command) is gibberish before and after gunzip. The only thing that changed that I can think of is the evaluation copy of Winzip on this work machine expired. I can't see how this would affect anything though. Also maybe related, typing gunzip in the folder without stipulating files results in the following error "gzip: compressed data not read from a terminal. Use -f to force decompression." 'file filename.txt.gz' says it's a gz compressed file. Any ideas about how I can go about troubleshooting this?

You could start by posting full detail of the commands which created the Zip archive, precisely how the archive was loaded onto your computer, the precise commands typed to explode the archive, and the exact error messages seen.

I stress the words precise and exact.

Please also post (for clarification):
Whether you used Windows or Unix syntax to explode this archive.