the only way I can access the alt menu is by having my camera (sx10) on the play back mode. Whenever I switch it to record mode I lose the alt menu.
- start the camera in playback mode with the PLAY button [>
- load CHDK with the "Firm update" menut item
- CHDK starts & shows the logo / splash screen
- now half-press the shutter button to switch to record mode, the lens extends...
- press the PRINT
button to enter <Alt> mode, then press the MENU
button to enter the CHDK menu
- now navigate to the RAW menu, call the "create badpixel" menu item
- this takes around 30 seconds, the display will be blank for some seconds
- now you can enable RAW and also DNG support from the menu.
After you've set up things in the CHDK menu, leave the menu with MENU, then leave <Alt> mode with PRINT...
Read more about using CHDK in the CHDK User Manual