PC slow,lagging and dropped fps in games.

Hey guys so the last few days my fps in World of Warcraft were like 20-30 max when they were 60 as of usually.
Well i figured as my pc slowed down also it would be my ram.One of the two slots of my ram cant even run on my pc now.It keeps beeping if i put that module on.I tried the other “working” module with memtest and it gave 308 errors on test 5 pass 1.but on pass 2 it didnt give any errors.
So i made an RMA from corsair got accepted – will send modules back soon.
Anyway my thoughts are these.Is it likely that the lets say halfworking ram is causing the freezes and dropped fps in games or could it be also a dying video card?
In addition,the ram module that now doesnt work on my pc it works fluently on my dads pc.
Also sometimes i turn on the electricity to power up my pc.When i press the button it doesnt give power and i see two led on my mobo to flash.One green and one yellow next to it.Note that they are near both ram modules and gfx card.Thats like the down right corner of the ram slots.
If i turn of the electricity and then back on and press the power button it works.Sometimes i have to try 3-4 times to get electricity on the pc.
So can i know what the hell are your thoughts on this?its kinda crazy:O

EDIT : – i checked the mobo manual about the LED.Its green when normal working conditions and yellow when overvoltage.The irony is that both light up!so which one is it?it could normally be overvoltage bt why green also light up?Also we are talking for the leds in the area of memory modules.
Answer #1
PSU could be on it’s way out.
As for games performance. that could be caused by antivirus software.
Try uninstalling the AV and running the game again to check for improvements.
Answer #2
Well i’ve been using nod before this happened and the performance was the same so no…as of PSU maybe.Waiting for more responses!thanks!
Answer #3
Because it wasn’t happening before doesn’t mean that it’s not the culprit.
It’s one of the first things to investigate.
Also run a memtest and disc check.
If you want to find out what’s wrong you are going to actually need to find out what’s wrong. nobody can tell you exactly what is causing the problem.
Answer #4
I said i run a memtest. Also my disk is 1 month old got a new one after my other one crashed.(pc was freezing up etc and disk was the faulty one,after that pc was superfast).
I know that dude its just that someone might have happen to come across something like this before.
Also its not the antivirus.It has nothing to do with dropped fps in any way and im sure of that!At least not Nod32