OK, ive got a PSU. One of the power cables form the PSU connects to my harddrive. ANd the cable which connects to the harddrive, has an adpater. So i plug in my fan into that adapter, and the fan has another adapter. so plug in anotehr fan onto that adapter.
Is it safe to plug so many things on the same power line? escpecaiily whne its getting the power through the HD? or it doesnt matter, and it wont affect how the thing runs...???

If u dont know what i mean, i drew up a digram

As long as the voltage drop isn't too much from device to device it should be ok. Use a digital multimeter to measure the voltages at the different connectors.

? i dont understand what ur saying. I just wanna know if i plug lots of things into one source, will it disturb the perfomanbce? like in my case will the harddrive not get the max power it needs? Or Its ok as the PSU is able to distrubiute the power the same if all the hadrware/fans were pluged intot their own source from psu.

Generally speaking the more devices you plug into a PSU, the voltage of the individual voltage rails will go lower(mainly the 3.3v/5v/12v lines). The use of a digital multimeter will allow you to monitor the voltage coming form the PSU.

If you can't understand that then I am lost for words.

Yeha ok, tahts more devices into PSU overall. how about devices into 1 of the cables (red,yellow,black) with adapters