Yeah, You can't OC a Dell, They put restrictions on their MOBO's.
You'll need to lock the PCI-e bus to 100MHz.
Set all voltage to Manual. Make sure stuff like your RAM is set to it's stock voltages, normally 2.2v, but I'd check that with your RAM's manufacturer.
Set the RAM Divider to 2.0 (or 1:1), the naming for this varies, but they're the same thing. This will half the speed of your RAM, so as you OC the CPU, your RAM's speed will increase, but because it's already been halved, you'll be raising it till it's at stock or just over, Make sense?
Slowly Raise the FSB in incriments of 10MHz. BOOT into Windows, Test for stability using something like Orthos (Set to Blend to test the RAM and CPU OC).
If you find that it isn't stable, add a little voltage to the vCore, I don't know what stock for your CPU is, but increase it one stage at a time. So, just move it up to next highest.
The max vCore for Intel CPU's is around 1.5v, Although, I wouldn't want anything over 1.46v for 24/7 use.
Most importantly of all, Watch your temps, Idle temps don't matter that much, just keep an eye on the load temps. Again, I'm not too sure on the temps for your CPU, but I'd say keep it under 60c.
Hope this helps. If I've missed anything, I'm sure somebody will point it out!
