Slot #2: Module Size 2048MBytes
Max bandwidth: PC2-6400 (400 MHz)
DRAM Frequency: 375MHz
FSB: DRAM 4:5
GPU: ATI Radeon HD 3800 Series
Memory: Size: 512 MBytes
Bus Width: 256 bits
Clocks: Core --
(ALL THIS INFORMATION WAS TAKEN FROM CPU-Z)
I provided all this information because I don't know if certain things on my hardware affect if I can overclock my CPU or MAX Overclock potential on my CPU.
So, I go into BIOS, go to Frequency/Voltage Control and it displays at the top "Current CPU Frequency 2,40GHz (266x9), Current DRAM Frequency 667MHz" (this is greyed out and cannot be changed, also this is what it is displaying before overclocking)
Intel EIST [DISABLED]
Adjust CPU FSB Frequency 
Adjust CPU Ratio 
Adjusted CPU Frequency  (This section is greyed out and changes as i change CPU FSB Frequency accordingly)
> Advanced DRAM Configuration [Press Enter]
FSB/Memory Ratio [Auto]
Adjusted DDR Memory Frequency  (this section is greyed out and I assume it would change as the settings above it get changed but I'm not 100% sure because I didn't mess with these settings.)
Auto Disable DIMM/PCI Frequency [Enabled]
Memory Voltage (V) [1.90]
SB Voltage [1.50]
Spread Spectrum [Enabled]
ALL I DID WAS CHANGE FSB FREQUENCY FROM 266 TO 333 SO THAT MY CPU FREQUENCY WAS 3000 (3.0GHz) AND WHEN I BOOTED MY COMPUTER IT DISPLAYED AN ERROR MESSAGE DISPLAYING "Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key" and would not boot up Windows 7, so I turned my PC off, turned it back on, went to BIOS and loaded optimized default settings, saved and exit and it was all back to normal (with no overclock)
So can anybody tell me what happened?
Temperatures are no problem because after overclocking the CPU temp only increased like 5ºC from 30ºC to 35ºC on idle.
I will provide a picture of what my BIOS looks like from factory settings, with no settings changed.
More about :overclocking intel core quad q6600 4ghz 0ghz
Try bringing it back to stock settings and seeing if you can boot. If not then your motherboard may have lost its configuration, be sure the boot drive is set as primary boot device. If this is correctly set try doing a 1 time boot select on start up (typically F9) and choose the boot drive. If this still doesn't work, boot to your windows disk and do a start up repair.
If you can boot at stock speeds then slowly raise the FSB perhaps 10MHz at a time until it won't boot or you reach desired OC.
By increasing the FSB you're also overclocking just about every other component in your PC, so sooner or later, problems will arise.
Put the FSB back to its original setting and see if the PC boots. If it does, increase the FSB back to 266 and check that the PC boots again. If it does, then you can gradually increase the FSB by 50Mhz until you encounter instability. If the BIOS allows it, you should lower the speed of the RAM to compensate for the increased FSB.
Whether you'll reach 3Ghz is unknown; overclocking is never an exact science, particularly if you use the FSB method.