An HP home PC boght in Peru 220 volts here its 110

Question

Yes my son broght a computer from Peru and it is 220 volts. There is no switch on the back by the electircal connection to switch to 115. I bought converters from Radio shack but the moniter said going to sleep like it was not enough power. How can I get this thing to work without spending to much or ruining the computer? Thanks John Lee Francis