'sleep' is not a recognized as an internal or external command, operable program or batch file.

We are using Ruby 1.8.6 along with Watir gem 1.6., and upon running a script that was written for Watir gem to create test orders for our website, the message 'sleep' is not a recognized as an internal or external command, operable program or batch file appears. It was working fine before we had to unsintall and re-install Ruby. Any ideas would be appreciated.