sounds like memory problem. Try reseating the memory, take them out and put them back in. They also can be defective Dell Inspiron 3520 RAM Replacement
What's the issue exactly, whether you can't open files or pop ups etc? It might not be a virus, but install malwarebytes (www.malwarebytes.org/) run full scan in safe mode. That fixes most viruses, malwares, spywares and such.
