A personal computer component diagnostic method is executed to recognize the status or potential problems of a computer before executing an operating system. The personal computer component diagnostic method comprising: calling a BIOS program; executing a component basic diagnostic program; and executing a component functional test after executing a predetermined step. The component functional test includes a CPU MSR/MTRR test, a hard disk S.M.A.R.T. test, a boot path test and a PCI device scanning test.