Well , if your heatsink had actually failed without you knowing , theres a good chance your cpu has overheated and died .
If your computer boots , i doubt there is a major issue with your cpu at the moment .
Whats the model of the cpu
If its a p4 3.2ghz i have reason to belive it only takes a min maybe less for those to overheat , good old information from one of computer hopes top posters there .
Tony