FWITW: i was able to add gpedit to Group Policy (see windowsseven forum tutorials) but "compatibility" does not show in drop down list of options - only one entry "16 bit (something)", nor does it show on any "Properties" tabs. so that effort was a bust.
i finally successfully re-installed Dell Sigmatel Driver "R99254" using "Troubleshooter" then picking 2nd option, which is NOT the "recommended" but - i think - asked 'troubleshoot program'. as i have upgraded XP -> W7 Home Premium clean install, and deleted all Dell Utility Etc partition., i ran it under "Vista" (not VSP1 or VSP2) and it worked! i now have sound back and Dev Mgr no longer has the [yellowtriangle!] on the "MultiMedia Audio Controller", also ""Sound, Video, and Game Controller" category has now re-appeared under Dev Mgr. the Dell R99254 driver for Sigmatel specs xp and vista but seems to default run as the xp version unless forced otherwise.
yes, it's a 2005 Inspiron 2200 w PentiumM@1.5 and maxed to 1.24G RAM, but it still runs and produces a good series of Windows problem-solving exercises to apply to my newer machines.