1) Remember, your old installation of Windows won't boot, because you've changed all the motherboard/CPU hardware. You need to do a fresh install of Windows so it can install the proper modules for your motherboard chipset, etc.
2) The Intel LGA775 4-push-pin design is a poor design, very easy to not-quite fully install. That would lead to the massive overheating you mention. Among other things, you need to install the CPU cooler *before you install the motherboard in the case* so that you can properly support the back of the MB with your hand as you push through the cooler mounting pins. You also need to visually verify that each of the 4 pins is all the way through. Other tips/cautions/instructions are here: http://www.tomshardware.com/forum/ [...] y#t1184072
Note also that after removing the CPU cooler for re-installation, you will have to clean off the old thermal compound from the CPU and cooler, and apply a small amount of fresh compound (AS 5 is widely available at stores, but there are others).

Yes. He already told you that you will need to reinstall windows since you switched boards. Before you even worry about installing the OS you need to fix the cooling. The cooler is NOT installed properly. Either one or more of the pins arent pushed through or you messed up the cooling paste or something.

When building a machine the OS comes last. First you put it together. Second power it on and see if it post and do a visual check to make sure all fans are working properly. Third is all the BIOS checks. Make sure the cpu is at a reasonable temp, proper clockspeed. The ram is at the correct speed/timings. If everything is as should be then install the OS. Then you can do all the finishing touches. Like cable management.

That is just a brief summary of stuff that a new builder should do.

How did you touch the processor with the 4-inch heatsink locked on top of it? The heatsink has 4 locking pins that can only be properly removed by squeezing the plastic tabs that have locked on the underside of the mobo. They are fairly tight, and it takes most people well over a minute to accomplish this after shutdown.

The fan consists of clear or black plastic spinning blades; the heatsink is the nonmoving aluminum finned metal underneath. The fan never needs any thermal grease. The top of the heatsink doesn't need any, either. Only the bottom, flat, solid portion that would touch the processor, and the processor itself, need coatings of fresh AS-5. Additionally, you should only clean old grease away with 90%+ isopropyl alcohol and lint-free paper towels or Q-tips. Never use plain water, and never reuse old grease or try to suck it back into the syringe.

What I'm mentioning is basic, but when reading your narration, I get this constant feeling there's a big miscommunication.

Firstly, to Wr, I read through the instruction manual of how to install the processor, and it has an easier way to uninstall the stock heatsink without squeezing the pins on the back of the board.

Secondly, to Mondoman, I checked the fan again and I still hadn't properly installed it. I re-read your article more carefully, and was able to properly install the fan.

Thirdly, it works! With the fresh application of AS-5, the CPU is idling at around 37 degrees Celcius, and I'm on the way to having XP fully installed. Thankyou for your advice in solving the issue, neen.