Why am I getting FPS drops?

[wytas2001]

System specifications:
CPU: intel core 2 quad q6600 B3 3.00ghz
GPU: msi gtx 750 ti 2gb (N750 TI-2GD5/OC)
MB: msi MS-G41M-SP20
RAM: Crusial 4gb ddr3 1066mhz (CT51272BA1339)*
HDD: wd blue 500gb (WD5000AAKS)
CPU Cooler: Deepcool gammaxx 300
PSU: Corsair CX550 grey 550w
OS: Windows 7 32bit

Old system specifications:
CPU: intel core 2 duo pentium e5500
GPU: nvidia 9800gt 512mb
MB: msi MS-G41M-SP20
RAM: Crusial 4gb ddr3 1066mhz (CT51272BA1339)*
HDD: wd blue 500gb (WD5000AAKS)
CPU Cooler: Intel stock
PSU: Unknown 400w
OS: Windows 7 32bit

*When I open "Computer>Properties" it says "Installed memory (RAM): 4,00 GB (3,00 GB usable)

So I just upgraded my PC and I'm getting FPS drops on every game. I need help finding the cause of these FPS drops because I can't find it. On my old PC I could play Counter-Strike:Global Offensive and League of Legends easily, but now I'm lagging. I tried cleaning and reinstalling GPU drivers, changing GPU back to the old one, overclocking CPU from stock to 3ghz - nothing worked.
What can I do to fix my problem?

Link to my Flickr profile where you will find all information you need:
https://www.flickr.com/photos/142762481@N06

I took screenshots of:
- MSI Afterburner in-game with and without lag
- MSI Afterburner Graphs that were running while I was playing Assassin's Creed 3
- HWMonitor while nothing was running (photos 1, 2)
- HWMonitor while prime95 was running "Small FFTs" test (photos 3, 4)

 

[power2015]

You should probably install 64bit Windows and also try to reinstall you drivers.

 

[wytas2001]

You should probably install 64bit Windows and also try to reinstall you drivers.

I installed Windows 7 64bit and new gpu drivers, nothing happened... 🙁

 

[wytas2001]

Update, I was dumb enough to miss that my motherboard has 95 fmb (supports processors with up to 95w tdp) and my q6600 b3 has 105w tdp, so cpu wasn't getting the power it needed then downclocked from 3ghz to 600mhz, and with that cpu usage went from usual to 100% as my pc was using all of those 600mhz. THE SOLUTION is to buy newer q6600 g0 wich has 95w tdp that my motherboard supports. So it would be working with no flaws.

 

[diellur]

Glad you sorted that out, and good work spotting it.