Comp used to work lovely but now...HELP!

[Blueprint]

So I have all new equipment with Windows 7 Ultimate, everything worked swimmingly for 6 months, but now it will just freeze for no good reason. Not a BSOD, just everything is stuck. It came on with more and more frequency to the point where now I can't get it to start up. Here's the equipment:

ASUS M4A77TD
AMD Phenom II x4 955
G.Skill Ripjaws 4x 2GB
XFX Radeon HD 5770 (HD-577A-ZNFC)
OCZ Fatal1ty 550W Modular PS
WD 750GB Caviar black x2

After not using it for a full day, I can turn on and get to the windows screen in safe mode, but then it froze as I tried to log in. Upon restart, it couldn't make it past the motherboard screen display during the boot, then the next restart the monitors were blank, although all the fans are running and everything seems to be powered up. Unfortunately, my case doesn't have a speaker in it so I can't hear the post beep.

I'm just trying to figure out where to start troubleshooting. Here's what I've tried:

• I tried booting with the hard drives unplugged and it got past the mobo screen, and stopped when it needed to boot the OS. Seems like the HDD is fine, so I plugged them back in.
• I had an extra video card that has worked for years so I swapped it out with the Radeon. Started the computer and it froze on the MOBO screen, then after a restart there was no display at all once again. Wouldn't appear to be the video card...

I don't know how to narrow the problem down. Any idea what might cause the freeze and then be responsible for the computer not being able to start or even put any video on the monitor? Any help is VERY VERY appreciated.

Thanks!

 

[Computers_Plus]

remove all your ram put in 1 stick at a time and try to boot the PC see if it's ram related