How to open/edit .dat files

Just wanna ask how to open and edit the .dat files, for creating mods. I don't have MS Access, but there was a post here viewtopic.php?f=273&t=28700 that says you can open them with free alternatives, but the links are missing. Can I ask what those programs were?
Meanwhile I tried also OpenOffice, but it doesn't work.
Thanks.
Meanwhile I tried also OpenOffice, but it doesn't work.
Thanks.