I have just bought decent spec desktop from a very credible seller.
Err - actually - it appears that you haven't !
If the "respectable seller" can't help, then try posting the make, model and spec here.
This may help those in the know to provide you with further ideas on how to diagnose the problem(s).
RAM modules are the memory chips installed in slots inside the computer.
They are (usually) upgradable items to give more memory (subject to limits),
but if not seated correctly into their mounting slots, thay can cause all sorts of weird and wonderful problems, as can faulty memory modules.
I get a long list of options about various operating aspects.
It would probably help if you were to post the details from that long list,
as it may hold clues to your problem....
Have you tried pressing the "F8" key on your keyboad during boot up ?
( Press the key repeatedly until something happens ! ).
This
might get your computer to start up in "Safe Mode" - Where only a limited set of device drivers are loaded,
and can then help in moving on to determine where your problem lies.
