I have a four year old Dell which is failing to boot up properly.
About a minute into the bootup, the monitor shows "Power Save Mode" and the machine turns off.
What could be causing this?
First thing to check in situations like this is if the machine is overheating. Boot into the BIOS, most BIOSes have a temperature monitoring tab. Let is stay there for a few minutes and see if it crashes or if high temperatures are reached. If so, open the case and clean the fans, the CPU's heatsink and the air ducts.
If you still have trouble, change the thermal paste between the heat sink and the CPU.