Follow the steps which are given below to check the power in Hard Disk Drive.
1) Adjust the multimeter by roatating the knob of the multimeter and set it to any DC voltage higher than 12 v and maximum can be 20v.
2) Switch on the system.
3) Now put the positive lead (Red) of the mutlimeter into Red wire from the back of the power connecter which goes to Hard disk and Negative lead (Black) into the black wire of the power connector of Hard disk.
4) Note down the readings. Which has to be +5 volts. Where as tolerance levels you can find from the above tables 2.1 and 2.2.
5) Repeat steps 3 and 4 for the yellow and black wires of Hard disk power connector.
And follow the above procedure to measure the power in the motherboard, CPU fan, Floppy drive, CD ROM etc.