Ok, so my PC worked for about 6 months and now it turns on, but the monitor light just blinks green like the PC is asleep

Before anyone asks, I've:

RMA'd my mobo (brand new mobo, different serial number)

tried a known good video card

tried all 3 sticks of ram in each of my 6 slots

took out the CMOS battery and purged all power to the board

tried different slots for the known good card

Also, all my fans spin and the fans on my GPU spin, including the fan on my PSU.

My specs are:
ASUS P6T SE mobo
Crucial 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600)
ASUS EAH4890/HTDI/1GD5 Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16
Intel Core i7-920 Bloomfield 2.66GHz LGA 1366 130W Quad-Core
Rosewill Green Series RG700-S12 700W
Windows 7 64bit Home Premium

At this point, any thoughts would be helpful before I just start RMA'ing all my parts till it turns on.

I appologize if someone has already had this exact problem and had it answered. I couldn't find something exactly like mine in the forums.

I appologize if someone has already had this exact problem and had it answered. I couldn't find something exactly like mine in the forums.

Since it is unlikely someone else has the exact same hardware, a new thread for your problem is the right way to go.

Fans spinning mean the 12V is there, but does not say anything about the required 5 or 3.3 volts. So I would suspect the power supply. Here's my canned text on testing them:

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

Swapping in a known good supply is a tried and trued method of troubleshooting, used for years even by pros. If you have access to a suitably sized, spare power supply, carefully remove the suspect supply and replace it with a known good one and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

Note the required voltage tolerance ranges:

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.

Wow! Wicked fast reply

My second question is:

Do you recommend I RMA my current PSU or just buy a new one? I ask because I've been reading of many other cases where Rosewill PSU's crapped out. So if I'm gonna get a new one, I can just cut out the middle man and use the brand new one as a known good to test anyways.

Thanks again

Rosewills do not have a good reputation. If you can RMA it I would. And if you can get a refund, instead of a replacement, and can choose what you want, I recommend choosing one from the "Reputable" list from here. I personally like Antec, Corsair, and Mushkin.

That said, you should probably try another monitor first, just to make sure it is not that one.

Yah, that was the first thing I checked.

My monitor is actually being used for my laptop right now...to simulate a desktop