I live in an attic and some summer days it can get above 100F (38C) up there. My older computers would "freeze" (ironic, isn't it, my computer is frozen while I'm soaking in sweat wearing nothing but a pair of shorts!) Typically I found that the computer would stay on but the input devices would not longer input (mouse, keyboard) but things that were running seemed to keep running.
My more recent computers seem to handle the heat ok. I dedicate a small household fan to circulate the air behind the PC in addition to the ones built into the case. My ASUS MB comes with its own monitor, and it has never read higher than 120F (49C) even on the really hot days. But I'm not overclocking, either.