well you can test the monitor an any PC made, to see if the problem is the monitor .
easy no? just one simple test. I guess a VGA cable.
That old monitor uses CCFL back lamps. that most at dead now.
after 10 years of service they are DEAD. most are. now.
Green means not sleeping.
when PC goes offline the Monitor tells you ,
lost signal, going to sleep, no sync, or out of range.
all monitors made 2000 to now do that. every one.
the OSD dead. test.
so when you turn the monitor on , and push menu button
in under 5 seconds, does the monitor show the OSD screen.?
it will do that even if PC is turned off.
The OSD is the tiny brain in the monitor. on screen display.
if you test the monitor with a flash light when it goes black with
and you see data, that means the CCLF are dead.
the do that, all do this now. dead, intermittent, stobes, or yellow for white screens. all do that at 20,000 hours. used.
click flashlight link here.
value if the monitor is $20 working , or $5 not.
so repairs are not all that econ101 giving this fact.