the shutdown issues are usually created by programs/drivers that do not cooperate with windos shutdown commands. So check what hardware was installed prior to these issues, if none, check which software was installed. Als be aware that several adware programs create the same kind of problem. Use Msconfig to prevent startup items loading the the next reboot. Then try shutting down. If all works okay, re enable a program or two at a time to eliminate the source, at a certain point something wil eventually pop up as the culprit, and if you don't need it, get rid of it.