Ramiro, CHM files have a different source file format compared to HLP files - they use HTML format instead of RTF. Therefore you cannot simply switch help compilers in order to create CHM files. (That said, it is theoretically possibly to write your own HTML/CHM topic generator using the extended PlexAPI in Plex 6.1) My suggestion would be to use a "Help Authoring Tool" (HAT) to create your CHM. If you search the web you will find several free, shareware and commercial HATs. I have found this site quite useful in the past:
http://www.helpware.net. On the Plex application side, you will need to map the F1 key in the Panel Designer and write some code to invoke the CHM file through the MS HTML Help API. For context-sensitive help, a useful technique is to use meta-code to pass in the surrogate number of the current panel as the id of the topic you want to display (or use some other unique number of your choosing). That way you only need to write your F1 processing once, in your standards layer. This assumes that the CHM has been written to also map topics to the help ids that match these panel surrogates. I know for sure that many Plex users have gone down this road before so hopefully others can provide some real-world experience.By the way, if you prefer to stick with HLP files they are still just about supported by Microsoft though an additional download is required on Vista.