File Associations

Even though virus scans show me as being clean, I have a strange problem that happened within the past couple of days. My file associations are completely wrecked. Not all, but a good bit. For instance, I wrote a short script in Notepad, saved with a .js extension and it now thinks it belongs to Dreamweaver. ???? Is there anything to look for, and/or how do I revert all to default? I got a feeling that it’s a registry thing, but don’t know where to look. Any help appreciated.