How to Check the RAM(SD,DDR1,DDR2,DDR3) in PC's ,whether it is Good or Bad?

There are some softwares you can use to test the memory by running the  test like Memtest etc.

Other symtom of bad RAM are bluescreen, beep codes, slow performance or not showing the RAM or exact size in the BIOS.

some reason of bad RAM base on my experience are your computer always restart, bluescreen show, not booting the system, the first thing i can do is i use eraser then i erase the dirt in gold plated area if the problem continues so have a bad RAM, or Bad Slot RAM