@nassoroshabani a steady Amber light is a power issue. Remove the power cord, hold power button in for several seconds to discharge the residue power. Remove your memory modules and try again. If that does not work, remove all PCI cards from your computer including the video card. Now disconnect all the drives as well. Remove the power cables and data cables form all of the drives. Now reconnect the power and try to turn it on. See if the LED changes it color/flashing pattern. If it has, replace one card after the next and one drive after the next. This should isolate the issue when it changes the color/pattern.
Most common failure on a desktop this age would be the power supply and then the motherboard. Download the owner's manual [https://dl.dell.com/manuals/all-products/esuprt_desktop/esuprt_inspiron_desktop/inspiron-530_owner's%20manual_en-us.pdf|from here] It does have a good troubleshooting section as well as a maintenance manual included.