Hi guys. First off, here are my specs. XFX 680LTi MOBO, Intel Q9550 Core 2 Quad 2.83G processor, 4Gb Corsair DDR3 ram, Nvidia 8600GT video card, SanDisk 480Gb SSD system drive, 2 x 1Tb WD Blue audio & misc drives. I'm running Windows 7 Pro.
Here's my ordeal. My computer won't boot up. It gets past the POST, to to the black screen where it says "Starting Windows" and then it freezes. Sometimes, if I restart it enough times, it will boot. Most of the time not, even if I start Windows recovery option after a hard power off. Most of the time it freezes up while trying to do that too! I've tried resetting the bios to default settings. I've reformatted the drive and reinstalled Windows several times. After that it'll work for about long enough for me to get everything installed, and use it for a week or two, and then it's back to the same thing. I bought the SSD because this problem started happening while I had my old conventional hard drive. I don't know where to turn. I know this computer is long in the tooth, but it was a good runner for about 9 years, before this started. Can anyone offer any insight, please??? I would be most appreciative!!
Thanks!!

EDIT: I wanted to add that the computer has never been online.

So, I've been reading that maybe it could be the PSU going bad. That could make sense, because several times I got a warning during the POST that mentioned reseating the processor. So maybe it's not getting enough power to it. The PSU is 10 years old, so I guess it's possible. Jeez, now I'm talking to myself.

Boot to last known good configuration. Google it

I would have said maybe hard drive failing, but you already swapped that out.  And clean installed Windows, so that is ruled out. 
 
First unplug all external cables and devices except for monitor, keyboard, mouse, power.  If you have any PCI or PCIe card installed other than GPU, pull them.
 
So that would leave these possibilities (in no particular order):
 
Power supply (try swapping in a spare).
RAM (if you have more than one stick, run with one at a time to eliminate that).
Check that all fans are running well, especially the CPU cooler.
Graphic card  (try a spare, if available, since no integrated video to test with)
Reseat the CPU heat sink with new thermal compound.  If that seat is loose, the CPU could be overheating.
 
Motherboard (sometimes it is just an age thing, capacitors wear out and start bulging and leaking).  This is probably the last resort, but if all else is OK, options are getting low.

Thank you guys. I'll try those things and report back!

If you're getting to the Windows logo, that's about the time drivers are loaded.
A corrupt driver can cause the system to freeze at that point.
 
If you're getting power related error messages, I'd start by reseating the main and secondary power connections going to the motherboard.

Thank you Jim. I was hoping you'd chime in. I'll try that. I haven't had a chance to mess with it yet (12 hour work days), but I'll be messing with it Sunday. I'll report back. I appreciate everyone's help!

For giggles make sure all your memory is seated too.  Probably a good time to check that all connections are good and cards are seated inside the box.

Great idea! Thanks! Like I said a couple times during POST, it gave an error I may need to reseat the processor or something else. Can't remember what the other thing was...

I had this a few months back. I replaced the PSU but no joy, eventually I narrowed it down to a bad RAM stick.
 
It's been fine since I replaced it.
 
What I would say, is that it was a real PITA to narrow it down as all the motherboard RAM tests passed.
 
The only thing that made me notice it, was getting a system report from the BIOS and it showing one of the RAM sticks running at a different speed to the others - it claimed to be a 1600 rather than a 1333, even though it was labelled as a 1333.
 
So abacab's suggestion of running the RAM one at a time is a good suggestion.
 
Other things it could be:

• Hard disk about to fail - I've had a SanDisk SSD fail and cause the PC to hang at the boot screen
• USB devices - Motherboards usually try to load drivers for all connected USB devices, and some devices will confuse it. At one point when my 18i20 was plugged into one of the USB ports, my PC would restart during boot up. Waiting until after it booted up before switching it on solved this temporarily, but I eventually solved it by swapping USB ports. Some motherboards also have an option to limit to keyboards/mice/drives.
  
  Try unplugging all USB devices before booting up, and see if this helps.