Thank you for contacting the Intel Communities.
You could be encountering with 2 different issues here.
1. Bad DIMM slots
2. Bad RAM modules
-Test each RAM module in each DIMM slot.
-Test the system with different RAM.
-Even if it has been working for a while, double check the supported RAM in the TPS for your Motherboard as well as the supported RAM by your CPU.
-If possible, test the RAM in a different computer.
These steps could provide you with a better overview whether the RAM or DIMM slots are faulty, or both.
Here you can find the TPS for your Motherboard (page 19 indicates RAM supported): https://downloadmirror.intel.com/20953/eng/DZ77SL-50K_TechProdSpec02.pdf
Here you can find your CPU and look for the RAM supported by it:
How to check the model of your CPU?
-Go to computer/This PC in the start menu and right click on any white space, properties.
-You should be prompt with the system information of your PC, there you would find the model of your CPU.
If you require any further information or support, feel free to contact us back.
Thanks for the quick and prompt response. As i said earlier i tried different DIMM slots using two slots at time, one at a time etc as initial trouble shooting (using one slot in channel A and one in channel B, using both slots channel A). Howe ever when i used only one DIMM slot (either of the channels with single 8GB Module) issue was not observed. One more observation here is due to some software limitations i had to use a 32-bit OS (as you know max RAM that can be addressed is 4G) even though both 8GB modules are used i din't ran into issues. My question here is could it issue with OS while addressing the memory or BIOS. As i said in my first comment issue is recurrent but not all the time when i switch on my PC it occurs. Hope this information can help you further.
Thank you for your answer.
I would like to know, have you tested the issue with a each of your RAM modules in a single DIMM slot? (it seems like the issue is not present in that scenario).
This would be to check if it is one of the RAM modules that is triggering the issue.
Additionally, please make sure that both RAM modules have the same model and specifications to avoid any compatibility issues.
To narrow down the issue as the OS, are you able to perform a fresh installation of the 32-bit version of your OS? Also a good way to check, if possible, would be to use a 64-bit based OS.
An advise to not loose all your information, you could unplug all the current drives from your PC and use a spare HDD to perform the tests related to the OS (fresh intall 32/64-bit based OS).
I look forward to your outcome with this.