3 monitor set up - 3rd monitor not working

I previously always had a 2 monitor set up, but recently I got a better monitor but still want to use the old one, I set up the tv and monitor to the dvi and the vga, the only one left is the hdmi, which is what i connected the 3rd one through, but no signal, the dvi is connected on my lg monitor, the tv is connected through the vga, and currently im trying to setup the asus monitor through hdmi, could someone help? These are my specs for my computer:

CPU: Intel core duo e7200 (OC to 3.2 G)
Motherboard: Colorful C.P43 X5 Ver2.0 with Bluetooth
Graphic card: Palit Nvidia GTX 260+ 216 sp (Processing Units)
Memory: 2 * 2G Kingston DDR2 800
Hard Drive: 2 * 160 G Seagate SATAII
Power Supply: Thermaltake Toughpower 700W with cable managment
Tower: Antec a600
DVD RW drive
Windows 7 Ultimate Edition