Raptor,
if your PSU has both an 8 pin 12v plug and a 4 pin 12volt plug, try swapping them out......
sometimes when the small 12v plug is not plugged in or does not have power going to it, it will look like everything is powering up on the PC except for the video/monitor will show with the yellow light ( standby mode light )
if your PSU lost its 12V function, then it might be the PSU instead of the Video Card
although, you said you heard the 1 long beep and 2 short beeps
hope this helps
edit: you can only try this swapping of plugs if you have the 8 pin plug in use originally...... if so, you can swap to the 4 pin 12v plug to see if the PC will power up the screen......... sorry forgot to mention this..... ( or some PSU's 8 pin plug comes in 2 pieces that will hook/unhook together! if your PSU is as such then there is no reason to try this possible troubleshooting solution )
TC