without Opening the Case
In the past, I have used a popular little utility called Belarc Advisor, which will tell you an amazing amount of information about your computer, including all of the installed software, serial numbers, amount of memory, etc. However, there is still a lot of information that Belarc does not report. For this missing information, I recommend that you also use CPU-Z. With CPU-Z, you can find out just about anything about your computer, and particularly that elusive statistical information like temperature, motherboard serial number, very specific memory information, and much more. You will learn important items like your processor name and vendor, processor package, internal and external clocks, clock multiplier, partial overclock detection, and processor features including supported instructions sets.
CPU-Z is available from http://www.cpuid.com/ and this site is where you can find many other useful utilities like HWMonitor (a hardware monitoring utility), among others. This latest version (1.43) of CPU-Z supports detection of the processor's core voltage, L2 bus width, support for two processors (in Windows NT/2000 only), and memory timing. Version 1.43 includes several changes such as Intel Skulltrail platform support (Core 2 Extreme QX9775 + 5400B MCH), Intel X48 chipset detection, AMD Athlon 64-LE 1600 and 1620 support, and other improvements.
Before I get too technical (too late), take a look at a picture of the CPU-Z interface below to see what all of this information looks like:CPU-Z is a free product available for download from CNet's http://www.download.com/ and you will find many favorable reviews of this essential tool. PC technicians need a tool like this to quickly sum up the hardware that a particular computer has. This utility, coupled with Belarc should make an excellent one-two punch, giving you all of the details you need to know about a computer without even having to remove the case.