I'm just copying this off my cnet post:

Hi, I rebuilt a gaming rig awhile back, and have been very happy with it so far. Since Orange Box came out today, and it was performing well, but not great. I decided to finally overclock my Intel Core 2 Duo E6550 from its default 2.33ghz to 3.0ghz or more I had been wanting to do this since I first built the machine. My friend and me decided it would be safe considering my new Zalman cooling system has kept the cpu at 27 Celsius or lower. So I went into my BIOS and cranked up the FSB to 1333 to 1334 just to see if my computer would do it (the multiplyer is set to 7 which is it's max) so my rig rebooted and gave a warning beep that something was wrong. I quickly cut the power and reset the CMOS. This time I retried the same thing only instead of having my cpu and ram linked in fsb, I did unlinked. This time it worked, so I went back and cranked the FSB up until the estimated CPU freq would be 2.40ghz it worked that time too. So I decided to go at it again, but go for the whole 3.0, after the BIOS saved and shut down, my system just stood there without booting, not even a warning beep. So I reset CMOS and clocked it to 2.60ghz which again did the same thing as 3.0. I have left it at 2.40 right now and this is my first time trying overclocking. What am I doing that prevents me from doing this? My hardware boxes claim they are built for overclocking, but what is restraining me? My specs are listed below

Thank You,
Josef

P.S. This morning when i started up my machine it would only go to the motherboard logo screen and then freeze I tried restarting twice and it wouldn't go past so I loaded defaults in my BIOS and it started up correctly so I'm back at 2.33 ghz.
 

Intel Core 2 Duo E6550
Fatal1ty Abit FP-IN9 motherboard with nvidia 650i sli chipset
2gbs of Kingston ddr2 800 ram
160gb seagate HDD
2 Fatal1ty XFX 8600GT g-cards that are sli enabled
a netgear wireless card
and a sound blaster audigy SE sound card

Need a better spec of the RAM, also have you read any articles on overclocking?  You can't jump from 2.4ghz to 3.0ghz.  I'd say check out Boa's guide to overclocking, however it may be dated, the same rules apply to any overclock.  Just remember the key to overclocking is patience.  A good overclock takes time to get.

mentaldisorder:

You can't jump from 2.4ghz to 3.0ghz

That's exactly what I did 1st try rock stable low temps... now if what you're actually trying to say is take it slow because he's an OC'ing virgin then I may tend to agree, but a 600mhz OC isn't considered huge and certainly not unattainable by any means.

There's no need to be scared of overclocking. In most cases, if you do something wrong, the system just won't post, and you need to reset the cmos. Keep in mind there are settings you want to disable when overclocking as well. Here's a guide to atleast teach you the minimum basics needed for overclocking.

http://www.tomshardware.com/forum/240001-29-howto-overclock-quads-duals-guide 

 It should point you in the right direction. But the most important thing, don't be afraid! I've been OC'ing for ages, and nothing has happened so for. Don't forget to loosen your ram timings to make sure you're not hitting the limits of your memory, and run them at a 1:1 ratio if you know how in order to make sure you're not hitting the ram limits as well.

If you need any help with anything specific, just post back and we'll gladly point you in the right direction.

 since you got nivida gpus why dont you download ntunes and overclock with that for a while to you get what you want it is really easy to overclock with this program and it will do a stress test also to see where it can go

Dont do Ntune just use the bios its much better... 

What have you done with your voltages? you need to up them bofre you OC, at least the Vcore the FSB core and if you keeping the memory linked then the memory voltage as well. 

 Very true Der Meister I don't trust any software to overclock anything buy my GPU.

Also, yes the voltages are most likely the issue. Try boosting them 1 notch above what auto is setting it to, do this one at a time. Nvidia chipsets are very very picky, some times 1.45 will work, but 1.40 and 1.50 are completely unstable.

Also make sure you disable "C1E" and "Intel Sidestep" to keep your CPU from throttling when you are idle. 

Keep an eye on those temps, and make sure they don't exceed 60 degree's at full load with Orthos running. To tell if your system is stable run Orthos for 24 hours. This loads your CPU higher than it will ever be loaded to, so you get max temps, and max stress.