You should have your HOA ban hardwood floors on 2nd story units. This is a common practice. Units with existing hardwood floors should have 80% coverage of area rugs with padding underneath. Ask your neighbor to remove there shoes when in their unit. You can also sue your HOA:
"Failing to control the types of floors installed in CIDs can result in a painful lesson. In one recent case a homeowner sued his upstairs neighbor and his association's board of directors because of an allegedly unreasonable amount of noise created by his neighbor's new hardwood floors. The board had approved the installation of the floors without investigating the potential for affecting the downstairs neighbor's quiet enjoyment of his property. The homeowner successfully proved that the hardwood floors created an unreasonable amount of noise and that the homeowners association was partially to blame for approving the installation. After a three week jury trial, the homeowner was awarded $162,000. The jury determined that the homeowner association's board of directors was responsible for two-thirds of the recovery."
If your interested in insulating your ceiling against the noise above read the following article. Scroll down to Soundproofing under existing drywall
http://massloadedvinyl.blogspot.com/ Also:
http://massloadedvinyl.blogspot.com/2005/06/green-glue-results-coming-soon.htmlSo basically you would want to attach MLV with foam backing to the ceiling this will isolate the ceiling reducing vibrations and block noise. Also, if you use Green Glue between the 2 pieces of drywall you can further dampen the noise and vibration from above.