The problem is solved, guys. The cause was that the VGA had blown its HDMI input and with the DVI output it works wonders. What I did was buy an adapter with a male DVI input and a female HDMI output. That was enough. Nothing was burned, neither the motherboard nor the memory. Everything is working. I just finished assembling everything yesterday. Thanks to a friend, we tested it at home and we cleared up the doubts. Wow, I didn't think so. Anyway, I have another 2011 motherboard up my sleeve, but I guess if I ever have problems with this motherboard, I'll have to replace it with that one. Anyway, thanks to everyone for the help.
Obs. In the part of turning on the motherboard manually, there's a button that says off and on. Apparently, according to my friend who read it in a forum, it should be on. So when we tried changing it to on, wuala, it turned on right away, recognizing the memory, CPU, etc. The only thing I had to do was reinstall the whole Windows 7 again, but that's history. As long as it works, I'm happy. Thanks again and I'm clarifying all this in case it might be useful to someone else someday.
It was a mistake not to tell you this because that's what happened to me with a 470 and 480. It doesn't always fail, but sometimes it goes black and doesn't work, so I connect it via DVI or DVI to HDMI. On an LG TV, it used to fail more often than on a Samsung, but HDMI fails.
The 480 has minihdmi as the output and I thought it was because of that output, but I saw normal HDMI failures too.
Although I thought you would have tried a different connection.
Regards

Gigabyte GA-990XA-UD3 - Motherboard (Socket AM3+, 4 x DDR3, 6 x SATA, 3 x USB with On/Off Charge technology)