So, I recently built a computer and after installing windows, I installed a cheap modem to register products and download drivers. Then I powered off to install a sound card, and I placed it in the slot previously occupied by the modem. The sound card installed fine, but now the modem wont work. When I place the modem in an empty slot (all 3) the computer turns on but wont get past a black screen. Can't even get into the bios. This also happens if I try installing a different modem or a network card in any of those slots. I reinstalled windows, but the problem is still here. I don't know why a modem that was working won't even allow a boot up. I thought it might be an IRQ conflict, but I don't know how to be sure. Any help would be great. Thanks in advance.