If this machine is over half a year old and has never been cleaned out, try that. Use a 25mm long bristle paintbrush, and remove the fans from your heatsinks for access to clean both the heatsinks and fan blades. Clean the entire mainboard and cards, including all chip heatsinks. Clean the case fans and their intakes and filters. Remove dust from inside the case. A small hand vacuum or a 20 to 30mm hose attached to a regular one is useful in collecting the dirt and dust, and a source of compressed air/gas can help loosen dirt, but be careful of static charge with that.
Finally unplug and disassemble the power supply. Clean the board and fan well.
Inspect the fans to verify that they all work. Check them for stiffness or sticking, excessive noise, and physical damage. Running each one with a 12v power source can serve as a check to trace down the source of a fan noise in a system. Include the power supply fan in this check. Stiff or noisy sleeve-bearing fans can sometimes be recovered with some 3-in-1 oil or similar lubricant, but often the best repair is to replace the bad fan with a new one.
Finally reassemble the components and system. It should work better.
The symptom sounds like the BIOS is hanging. Insure that your BIOS setting for 'Floppy seek' is off. You may wish to reload BIOS with 'failsafe' values and reboot, then re-enter BIOS and change the NumLock, floppy seek, and other settings. Also try running with the floppy disconnected and the controller off; if this results in normal startups, replace the defective floppy.