DVD Drive not working on my dad's computer

Yesterday I went to see my dad for Father's day. After going out to eat, we went to see my aunt. He had given her one of his computers. A couple of months before he gave it to her the DVD drive wasn't showing up on the computer. It was present in the device manager, but it wouldn't start, and the error that it showed led me to another blog, Computer Repair Guide. The solution to the error message was to remove certain entries from the registry, specifically from

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}

I applied the solution and it worked. But it wasn't working at Jean's house. When I checked, the important entry (LowerFilters) was still gone, but the one that it said really didn't matter (UpperFilter) was there, so I deleted that, and it worked again.