The reason it won't boot is because when XP was originally installed, it was configured to work with the hardware (including MB and Processor) it found at that time. Changing the hardware without re-installing the OS means when it tries to communicate with the hardware it thinks you have it all falls down.
You need to re-install XP on your new Hard Drive, which will then be configured for your new hardware, following which you should install your chipset drivers which came with the board and processor and drivers for all your other hardware too.
Normally, you would then have to re-install your programs so the new OS can put their data where it expects to find it - it's on another drive at the moment so just navigating to the original install directory and running the executable will probably result in nothing happening at all or very unpredictable results.
However, if you look HERE
, there appears to be a program which claims to be able to transfer installed software from one computer to another, if you no longer have the software CD.
Worth a go anyway.
Hope it helps.
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