It all depends on two things;
1) That you can go into BIOS Setup, and change parameters.
Parameters such as;
A) The Front Side Bus speed. (FSB), or
B) The Voltage for the CPU (Processor), or
C) The Multiplier for the CPU (Processor)
Or there may be a Soft CPU option available for the above, in BIOS Setup.
Be aware that overclocking the Processor will also step up the FSB. Ram memory, and expansion slot devices, will cease to work if the FSB is too high. (Front Side Bus,http://en.wikipedia.org/wiki/Front-side_bus
408MegaHertz to 1008MegaHertz?
That's a big jump. I do not think that processor in this technology age, is capable of overclocking this far. Plus IF it does, will not continue.http://en.wikipedia.org/wiki/List_of_Intel_microprocessors
Heat will be a Big issue for one.
The pathways inside a processor are based on the nm architecture.
NanoMeter. 1 Billionth of a Meter.
[ Your processor was probably in the 250nm architecture technology. Today's processors are down to the 22nm architecture ]
With too much heat there is Electron Migration. The electrons jump off, or Migrate, from the circuit trace they are on, over to a wrong circuit trace.
Causes the processor to burn up.
Secondly there is also a limit on the performance of a Processor. Asking for almost 2 and a half times the factory setting, is asking for too much.
Plus the Processors are tested at the factory, and sent out. They only have to fall within a rather broad set of specifications, and can be considered okay for the consumer, or computer manufacturer.
The Processor you have may have been on the Bottom of the test range. Even if you have knowledge, of someone else getting this kind of performance out of the same model, it may be that theirs was one of the ones, on the Top of the test range.
Overclocking is done in SMALL increments, THEN tested to see if the computer works fine, over a 24 hour period.
Change the Voltage?
Change in no more than a .2 Volt increment. Then the 24 hour test. Everything's OK? Move up .2 Volts. 24 hour test.
Remember, Ram Memory operates at approximately Half, of the Processor's FSB.
The expansion slots are a lot lower.
Change values (Parameters), such as Voltage for the CPU (Processor) for one, and you change everything.
Too much, Ram Memory, and anything in an expansion slot, will not work.
What Processor is it?
What motherboard name and model number? (Or what computer manufacturer and model number )
Post back in a Comment.