I am going to make a suggestion that I might get yelled at for
What i did with my Dell to overclock it was to do a BSEL Pin Mod
link here
http://www.overclock.net/intel-cpus/341123-intel-bsel-vid-mod-guide.html#post3980695
It involves using a circuit writing pen (bought mine at RadioShack $10)
You use the pen to "draw" a jumper from one pad to another on the CPU
It will "bootstrap" or raise your FSB
In my case I had a 800/1066 MHz FSB so I changed my
E4500 2.2/800 FSB to 2.93/1066 FSB
It has been running cool and stable for over a month 24/7
Before that I had a E4300 1.8/800 at 2.4/1066 running 24/7 for 4 months
The mod seems scary but it is not
Looking at the specs of your XPS 720
http://support.dell.com/support/edocs/systems/xps720/en/OM_EN/index.htm
I am pretty sure your motherboard supports 1333mhz FSB
If you did the mod
Your chip
http://ark.intel.com/Product.aspx?id=30790
has a stock 10 x 266 = 2.66 setting
with the mod you would have
10 x 333 = 3.33 GHZ
there is a possibility it might need a voltage mod
but
I doubt it
With a steady hand you draw the jumpers
then let it dry for over 2 hours or more
then reinstall using a good thermal paste
instructions here
http://www.pcstats.com/articleview.cfm?articleID=2231
might be a different heatsink/fan
refer to Dell docs for removing the assembly
then apply paste
http://www.arcticsilver.com/intel_application_method.html#
Artic Silver 5 is a easy to get and proven paste
though there are newer and better pastes out now
MX-4 is good for Artic Silver
Tuniq makes some great pastes
as long as you are careful not to jump the wrong CPU pads by accident
(use magnifying glass if you have to)
then the worst that would happen is you wouldnt POST/Boot
but you could clean the jumpers off the CPU with Isopropyl Alcohol (70% or better)
and it should boot up no problem
Be careful not to get any in pins in LGA775 socket
good idea to blow out socket with hair dryer or canned air
I have done this successfully and have read of many others doing it
also
hopefully you would end up with a C2Q @ 3.33/1333 FSB which would be a big
improvement
Warning
Do this at your own risk
With any modification there is a risk you have to accept