My startup sound also does not play. I notice that my speaker icon in the taskbar doesn't appear for some time as other programs are still loading. Antivir, malwarebyte, sandboxie, and a few others load first. By the time the speaker icon appears, windows is well underway and fully loaded. I guess the speaker loaded too late so it missed it's cue. If you create other users, all those programs won't load so your sound will play. I have checked online and there doesn't seem to be anyway to load the sound driver
earlier. I am running XP pro but the issue you are having is probably the same one.
Just try to find out how to load the sound driver earlier in the boot sequence.