In a command prompt either type / paste
@set PATH=C:Program FilesCommon FilesMicrosoft Sharedweb server extensions12BIN;%PATH%
for SharePoint 2007
@set PATH=C:Program FilesCommon FilesMicrosoft Sharedweb server extensions14BIN;%PATH%
for SharePoint 2010
Edit : this will be lost when the command prompt will be closed, so you’re better of editing the environment varialble to add the bin path to it by going to
Control Panel > System > Advanced System Settings > Environment Variable > System Variables > Scroll to Path and click the Edit button and add ;C:Program FilesCommon FilesMicrosoft Sharedweb server extensions12BIN (don’t forget the semicolon separator !)