PSU dead? a few problems with my PC on gigabyte p35-ds3

[exxcellent]

i have been using my laptop because my desktop has been giving me a few problems for a few months.

first of all, my desktop always give me 1 long beep and followed by 3 short beep and there would be no image appearing on my monitor. sometimes to fix this i have to reseat my rams OR i have to reseat my ati graphics card (pci-e). is the problem here with my motherboard or ram?

second of all, i realise that whenever i connect my usb wireless lan card to my pc it sort of hangs my pc. i still do not know if it is my usb card that gives me the problem. is the problem here with my usb lan card?

thirdly, my pc nowadays auto restart itself. like just now when i try to back up my files by transferring to my external harddisk, my cpu tower will give off the "power off" sound and then boot itself and give off "power off" sound once more then restart once again and finally have the 1 beep sound that resumes booting up of window. is the problem here with my cpu/power supply unit or even the problem with fan?

i would appreciate if someone could answer my queries.

 

[exxcellent]

any help would be appreciated? my gfx and cpu temp are decent

 

[Leeky]

Can you get another psu from another computer in the house to see if your PC will boot and run?

Its usually the fastest way of diagnosing a faulty psu. I'll leave those considering more knowledgable than me to recommend other action based on your beeps.