Whats wrong with my dell Optiplex Gx 270?

I have a solid amber or yellow light . I replaced the power supply and re-seated the processor and memory sticks and I still have no video the only thing I cant do is turn it on and by holding the power button.
My specs are

Intel Pentium 4 2.6GHZ Processor

1GB Memory

40GB Hard drive

CD Drive and Floppy Drive

Intel Integrated 2D/3D Graphics Accelerator( VGA Port )

Realtek Integrated AC’97 Audio(SoundBlaster Compatible)

Intel Pro Integrated 10/100/1000 Gigabit Ethernet

Windows 98SE Loaded

1 Parallel, 1 Serial, 8 USB (2 Front/6 Rear), 2 PS/2, 1 VGA, 1 RJ-45, Audio Jacks

2017-11-08T01:48:37Z

"I can turn it on and off by holding the power button"

2017-11-10T04:05:15Z

I also hear the hard drive working

Ahtsham2017-11-09T17:44:00Z

It means your motherboard is expired

?2017-11-09T03:15:42Z

Had the EXACT same problem with my PC after incredibly heavy use in a 12 month period. Replace the hard drive and reinstall windows. ;) That'll get it to work again!! :D

AnDi2017-11-08T03:39:51Z

After 15+ years... and running win 98SE
Impressed that the hard disk is still working - perhaps it isn't .. and it can't boot

Seriously, time for a new one.
Win 98SE wont be protected against any current internet exploits
and not sure your browser can cope with any pages..

in fact what DO you use it for ?

Dave2017-11-08T02:18:37Z

Why on earth would you replace the power supply on a 19 year old computer??? What a waste of money.

It's dead. Get a new one.