Is my external hard drive powerful enough to run my macbook without any working internal harddrive?

A couple months ago my laptop suffered a crippling blow to its internal HD. I assessed the problem and fixed it by installing my software disc to a 500 gb WD external HD and worked with it this way for about a month. Now the same has happened with the external HD and I can not access my Macbook. My question is if I shell out for a new internal hard drive will it hold the same fate? or was the external WD Hard drive device just not powerfull enough to run a computer?