If the errors are just with one memory module, try swapping the other one into the socket that's showing the errors.  If it's clear of errors there, you're looking at replacing just one module.  Depending on what the other errors are, that may make sense.

If the errors are with both modules - or the errors show up on the module without errors when you swap sockets - it's the mainboard that's bad, not the memory.  And on a system that's on the order of 11 years old, repair makes little sense - it's time to replace the system.

If the errors are just with one memory module, try swapping the other one into the socket that's showing the errors.

how do i check if my errors are with one memory module?

how do I swap what?

the order of 11 years old, repair makes little sense - it's time to replace the system.

I purchsed my laptop 4 years ago as i start college. i'm still in collge 

i have dell xps 9550

what is module and what is socket?

i googled but can you please specify?

You may want to start by posting your system model number.  The XPS 1555 your userid implies is a 2009-model system.

In general terms, open the base cover and test the RAM one module at a time, and in each socket.  It's highly unlikely two modules will simultaneously fail.

Remove the base cover (you'll need a small Torx driver).  Service manual here:

https://www.dell.com/support/home/us/en/19/product-support/product/xps-15-9550-laptop/docs

what do you kean by modulemand socket? do you mean Ram by module?and a soxket is where it holds ram?

Module means memory module.  Socket is the connector between the mainboard and memory module.

In all likelihood, you have two modules.  They're side by side on the system board.

1.  Remove the base cover.

2.  Remove one module.  Replace cover an test.  If the module fails, move it to the other socket.  Test again.  If it fails in both sockets, it's likely bad.

3.  Test the other module in both sockets.  If it tests OK in both, you have just one bad module;  replace it.

4.  If both modules test bad in one socket - or both modules test bad in both sockets - odds are overwhelming it's not the modules that are bad, but rather the system board.  Depending on the CPU you have, replacing the board will run somewhere between $300-700 -- and that's if you do the job yourself.

My system is just 2 year old.. Still I faced the issue of Error code - 0122...though system was not fallen and nothing malcious was installed