It's still there. Click the download button at the top of the page then "FMOD 3 Programmers API" under "Links" at mid-right on the page and you get here FMOD music & sound effects systemas 3.75 seems to have walked the plank, and nothing on their website references windows mobile.
Since you posted your query, http://www.basic4ppc.com/forum/additional-libraries/4686-powernotify-beta.html#post26860 has introduced a library that allows the backllight to be turned off or on. Not the same as adjusting it, but if that is what you really wanted...This might be a very stupid question, but i'm totally new here. Is it possible to adjust the screen brightness using basic4ppc code? And if it's possible, how do i do that?