Very slow computer!!

Ok so recently my desktop has been running very very slow. I just turned on my computer this morning and the computer started up quickly as usual and everything was fine, but after about 1-2mins after the desktop loaded, the computer started to actually lag, like my cursor was sliding a second behind the actual movement of my mouse, the icons on the desktop *when waved over* were also not responding instantly, like the glow behind the icons were lagging as well. Even as far as closing my windows, the window doesn't close as quickly, you can see the fading effect a little bit choppy.

Yesterday, I was playing Tera Online, which uses the latest Unreal Engine and it is notorious for having memory leaks, which actually did crash my game, but everything was fine and I went to play OSU after and the game had no problems. However the next morning all of the lag started for no apparent reason.

I have tried to check my memory and my computer detects no problems with my RAM. I have also checked and monitored my task manager and nothing seems to out of place or unusual. I have scanned my computer with my Windows Defender and I have also done disk clean-up. My next steps are to try to boot in Safe Mode and use CCleaner and Defraggler, but I highly doubt that it will help.

PLEASE HELP! I really need to find a fix for this problem, it's driving me mad with lag so bad that it makes a windows 98, 2000, and ME 100x faster!


My Specs.
Windows Vista 32bit Home Premium
AMD Athlon 64 X2 6000 3.2Ghz
3GB DDR3 RAM
Nvidia GeForce EVGA GTS450 Superclocked