This matters a lot. Between 6H98 and 6L38 there was a massive update to Inform that changed a lot of syntaxes. If you want to keep working on your project without updating the syntax, find a copy of Inform 6G60 for Windows and use that. (6H98 is just 6G60 for the Mac–the original 6G60 Mac application had bugs that 6H98 fixed, but that doesn’t apply to Windows.)
If you want to change it to the new version, check out this thread or just post some of the problems you’ve been having. (There are a few standard ones: “change… to…” usually needs to become “now… is…”; any reference to “indexed text” should become “text”–anyone think of any other ones?)