Monitor Video Graying Out Or Having Lines Or Blocks

I have a flat-panel Dell monitor that I've been using for years with my Windows 7 - 64 bit system.

A few weeks go, I powered up and went to do something else while it booted up. When I returned, the monitor just showed a pearly gray screen and not the desktop. I swapped it out for an old CRT monitor I had sitting around (for just such emergencies). The CRT worked fine. I also connected the FP to an old tower that runs Windows 98. The FP worked with the W98 system. I put the FP back on the W7 and it worked a few days, but after I had it on a while, the video started breaking up and slowly went to a faded-out video with colored lines (see screen shot). I turned the power off to the monitor and back on a few time - each time it would show a different pattern of lines, but no desktop.

I tried the swapping routine again with the same results, then put the FP back on the W7 computer. It worked a few days when the video suddenly just broke up into small black and white squares in an irregular pattern. I am now back using the CRT. The FP still works with W98.

The FP has 2 captive cables (so I can't test those individually), one has a small blue plug on the end (which is what I use to connect the monitor to the computers
- see photo), the other is a little larger and light gray colored - I don't know what that's supposed attached to - it doesn't fit into anything on my computers, so I never used it.

What is the most likely problem?

 

BTW - this is the other FP monitor plug - the one not used.

 

What are your CPU and GPU temperatures like on the Win 7 machine?

 

Here's a screen shot of the temps.

 

The temperatures are fine.
As a test, connect the monitor to the Widows 98 PC and see if it's fine after a couple of hours.

 

I did that and it was fine on the W98 system.

 

You make no mention of how long the monitor works when connected to the Windows 98 PC. If you're satisfied it will work indefinitely, then the problem is with the Windows 7 PC.
It's not a driver problem. Having another look at the temps - the motherboard's temp is higher than that of the CPU which is not a good sign. The CRT monitor works, but does it work for days without problems? Also, CRT monitors are more 'robust' than LCD monitors.
The problem is probably motherboard-related. Ideally, connecting a different LCD/LED monitor will (hopefully) yield an answer.

 

I left the FP monitor on connected to the W98 computer for several hours and it was okay. I've been using the CRT with the W7 system for several days and no problem so far.

 

Here's a pic of a monitor exactly like my FP montior, front and back.

 

It's a picture of a CRT monitor.

 

No, it's a flat panel! Here's a side view. It's a Dell, Model 1501FP, according to the packing info.

 

OK. The pictures in post #9 where misleading.
All I can suggest is...