When i turn on my CPU, it shows correctly "Windows Loading" then gets NO SIGNAL on screen and my CPU fan starts to spin fast. Then, I click on the reset button on my CPU to start back again my CPU, it shows to "Start Windows Normally" then it works fine
What you have is a system that will not boot cold (initial power on), but will boot warm (a reset). If that is a consistent pattern, its likely a bad voltage regulating component and you have them on BOTH your power supply and your motherboard, so its not an automatic fix.
A reset is a more friendly booting environment because all capacitors are already charged and any small amount of moisture is already evaporated from the previous boot. On a cold boot neither is true. When a motherboard OR a power supply goes bad, it may manifest itself with inconsistent voltage which results in reboots or freezes or system lags as devices are briefly underpowered which screws up the windows driver and causes a freeze or reboot. This can happen at cold boot or just while you are using the system. When you say that your fan speeds up intermittently that can be from hardware disconnecting due to unanticipated power fluctuation and windows then needs to redetect and reload the driver.
An easy thing to check is to make sure the fan inside your power supply is still working. You may need to stick a toothpick just slightly into the power supply vent to feel it moving, or use a flashlight. If the fan is dead, your power supply is certainly the problem here. If the fan is fine, my guess is that either your motherboard or power supply is dying. There is no way to be sure. Your system is 10 years old and was made with a power supply and motherboard that are below the quality of retail power supplies and motherboards (that's one way Dell and HP make money, they use parts that are barely viable, knowing they are going to burn them in in-house as a system and can just discard them if they fail).
One way to test power issues is to intentionally underpower the machine. Use memory settings that are slower, remove any pci or pci-e cards, remove any extra hard drives, or any of the above. If you are stable after that, you probably have a power issue.
