Please note that not all mobo's with 775 socket is support intel core2 family cpu (because of chipset and FSB compatibility), you better check your motherboards cpu support from the motherboard official sites...
I recommend Biostar TPower i45 for your quad core CPU, its support up to 1600 FSB with intel i45 chipset too... ^^
Sorry I couldn't find your motherboard specs either...
but in my search result (with google) the foxconn LS series is come with 478 socket... Just to make sure maybe you can see your mother board userguide book that came with the motherboard package and look if there is any information about socket type, chipset type, maximum memory frequencys, and max FSB frequency.... if you want to upgrade ur cpu to intel quad core series your motherboard must have minimum requirement like below:
1. Chipset intel P31/P35 or above...
2. Support FSB minimum of 1066...
3. Support DDR2 533/800/1066...
Let me know if your Foxconn LS-36 has the minimum requirements .... If ur motherboard have the minimum requirement you can upgrade ur CPU to quad core, but maybe bios update will be required... sorry for my language he....
Your system specs are insufficient to be able to help you without more info.
Step 1. Download this program (it's free) cpu-z 1.52 ,if you don't know if you have a 32 bit or a 64 bit operating system download the setup & install from that.
If you prefer not to install it & would rather run it without doing an install, download the 32 bit zip or the 64 bit zip and extract it using winzip or winrar or 7zip to a folder that you can easily find (ie. the desktop) and double click the exe file inside.
You can download it from here http://www.cpuid.com/cpuz.php file size is approx 1.7 MB
After install, start the program, there are only 2 tabs up the top of the program that are of interest "CPU"(your processor specs) & "Mainboard"(your Mobo specs)
What we are really looking for is the chipset ID ,BIOS revision & Mobo revision.
Here is a screenshot of what it will look like [IMG]http://img269.imageshack.us/img269/1338/cpuz3.png[/IMG]
Step 2. What version of windows are you running ie.WinXP,Vista,Win7 & with what service pack?
Not sure how to tell? Right click My Computer & select properties, this will make the System Properties appear ,then select the tab marked General.
Then just read the information under System.
Between the info from Windows & Cpu-z we can probably get a accurate idea of what processor you can use.
Otherwise go directly to Dell Support here
Make sure you use Internet Explorer to click on any of their links, Firefox version 3.5.3. had compatability issues with their links.
They have 2 links worth checking out "Parts & Upgrades" "System Configuration Information".
They also have a program called "Dell System Analizer" which can probably point you in the right direction.