It stopped working properly because of the Windows XP install on the disc. It is designed to detect any changes in your install system. It does not always detect the changes but it is supposed to.
If it detects any change in the system, such as motherboard, cpu, hardware configuration, chipset, video card, or anything other than a memory change, it is designed to shut down or freeze.
Read the EULA that is found on the Microsoft site, and comes with each and every Windows Disc. It tells you what your rights are. You can also find a lot of information on the Microsoft web site.
Microsoft's legal position is that you do not own the Windows XP. You merely are licensed to use the WXP product key on one motherboard. When the motherboard dies or is changed, the license expires. You can talk them into a fix, but only if you do not have a history of making several changes.
A clean install will not be detected, but if the product key has been used more than three times in a year, or more than twice recently, they will give you a hard time and require you discuss it with them over the phone. If you go more than a year without an install of the product ID, they will allow a clean install... but they do not have to do so.
OEM WXP and Academic WXP installs are the most difficult because there are so many discs out there. Microsoft will not allow multiple installs on those two versions.