Computer freezing up when CPU usage is low

       My Dell Inspiron is a rebuild but the newest computer I've ever owned.  I'm used to certain programs being too much to handle due to memory issues and using basic functions to get around this, but although this machine has more capabilities the basic functions (like CTRL-ALT-DEL) are compromised.  Task Manager takes so long to load it is not useful in ending unresponsive programs or finding out what is wrong.  Programs often freeze to a halt when Process Manager says the CPU usage is quite low, and sometimes the computer freezes when no programs are running at all.  Online I have trouble loading websites that looks like a bandwidth issue, but there is nothing wrong with my DSL connection and during these hangups a program like notepad or solitaire becomes unresponsive, something a connection issue should not cause.  I get a blue "dump" screen that forces a restart.  I used to trust Task Manager to be able to diagnose problems like memory maxing out or a bad process, but this one leaves me completely in the dark as to what it's doing.  I'd rather increase my understanding than just replace the PC or get it wiped because that kind of solution has not educated me as a user.  ty