i'm having puter problems

my computer is randomly shutting down or rebooting. POOF! gone. it won't stay running. i'm pretty sure it's a hardware problem. the power supply unit is making a faint buzzing noise when off. i think i can fix it.
one thing i'm not going to do is buy a new computer with microsoft on it. absolutely, positively, no way in hell am i going to buy a microsoft computer. i'll spend ten times the going rate on replacement parts or learn how to build a machine myself before i'll give microsoft another dime. hardware manufacturers really need to start supporting GNU/Linux on a larger scale. when they do i'll consider buying a new puter.