first - you should to reinstallation, to keep the system clean - but most likely it will run "somehow" with new hardware... (after getting rid of old drivers and installing the new ones)
on the other hand you do not need new key, if you just hange "defective" parts of a computer and explain this kindly to MS hotline.
But this is assuming, some of your old components are overheating, or the lan chip / sound chip defective - which makes your
change reasonable.