This is a genuine Dell motherboard.
This motherboard has been thoroughly tested by our experienced technicians and is guaranteed to work in your Dell OptiPlex 990 small form factor.
I arrived to work on a Monday (4/25/16) to find that my computer was DEAD. Dell tech support gave me model numbers for the power supply and motherboard that I needed to get because Dell did not have these in stock.
I googled the model numbers and found Discount Electronics. On Wednesday (4/27/16), I received power supply and motherboard. I called Dell tech support again (spent about 15-20 minutes) to get a link to a video or a manual instructions so that I could replace the parts myself. It wasn't too difficult because I labeled each wire that I pulled out. The only tools required was philips head and screwdriver. My PC was up and running in about an hour. It has been a week already and it still works.
The only thing that would have made this easier is if directions on how to replace were enclosed or if a link were available. This would have saved me a little time.