I have a used MegaMicro PC with Abit BE6 motherboard with five PCI slots. Only two PCI slots are used by modem and 3Com NIC. When adding a COMPUSA wireless card PC would nor even powerup. When I removed the COMPUSA wireless card the PC would powerup and bootup normally. I tried playing with the BIOS setting the PCI setup manual or auto and load defaults, still does not fix the problem. The power supply is rated 250 watts (maynot be the original.) Thanks in advance for your help.