Well guys im having MAJOR pc issues. it all started with my pc freezing and then my monitor went black, my monitor still had power (was not on stand by) while it was just a black screen. i would have to restart my whole system so use it again. The temperature in my CPU is now usually kinda high, when i 1st bought it it was around 23-30 degrees Celsius , now its even reaching 70 degrees Celsius, i have 3 fans in my CPU and still its has high temperature.
the new problem now is when i try to go into safe mode, it lets me log in and then my system just shuts down. i need my system for work since i do photography, but i really cant even run much of my program without my systems CPU usage hitting 100% and just shuts off.

my computers specs are:

Computer:
Operating System Microsoft Windows XP Professional
OS Service Pack Service Pack 3
DirectX 4.09.00.0904 (DirectX 9.0c)
Motherboard:
CPU Type Intel Pentium III Xeon, 2500 MHz (9.5 x 263)
System Memory 3072 MB
Display:
Video Adapter VIA Chrome9 HC IGP Family (128 MB)
Monitor Dell E173FP [17" LCD] (U493154J2Y4U)

Motherboard DMIMOBO: BIOSTAR Group P4M900-M7 FE


PLEASE HELP!!