I know this is a touchy subject, but my over-qualified PC recently has some problems with the graphics. Basically, I will start the game off at a pristine cap of 60 fps, and that would quickly decay to a steady 5 after about 5 to 10 minutes. Changing the performance options in the game just changes the initial fps. Putting it on ultra settings reduces starting fps to 40, low starts off at 60. No matter what, they decay to unplayable levels. I have defragged, cleaned malware, spyware, and viruses with MacAffee, Microsoft Endpoint, and Malware bytes. I have ran the game through the reccommended GameBooster. I have tried CleanMyPC. I have updated ALL my drivers. Nothing helps. I was playing happily 1.5 months ago with no issues on this PC.

My specs are:
Windows 7 Enterprise 64 bit
Intel Core i5-2540M CPU @ 2.60 GHz (quad core)
4 GB RAM
NVidia NVS 4200M (64 bit and 1GB internal memory)
175GB free of 500GB hard drive (just in case)

I am tired of playing like I own a piece of **** pc from over 10 years ago. My brother even uses a laptop from 2000 and gets a steady 24 fps, which beats this. I want solutions.

I got kinda the same problem but idk must be a patch thing i use to have 60 fps on max quality and now ive been getting only 10-20 fps on max quality had to make everything low just to get 20 fps for some reason i think it might be because of the new patch

Yeah, I used to have 60 fps all the time at highest settings, but now I drop and around 20-30. I changed the settings to all low and it didn't change anything. Not sure what is going on...

I played last night and it was fine (I usually play with everything maxed and I'm locked at 60fps). Just started a game today and the game started at UNDER 10 FPS.

I am having this problem for a couple days now. I have repaired the game but the FPS problem continues.

Edit: It is something about memory, when the game doesnt show FPS issues it uses about 150k less...

Yea I have also noticed all the League related programs absorbing some hefty memory usage. If I recall, this started happening to me right after the graphical update for a new sleek HUD and more readable font...

Enterprise Edition doesn't run games very well from my experience. I would recommend reformatting to a different version of Windows 7.
There's also currently a bug with Windows 7 and most Intel-based processors occurring with "Superfetch" and it's hyperthreads. Try turning that service off and see what happens. This may perhaps solve your "decaying FPS" issue.
Your RAM and hard drive should have no to little effect on your frame rate.

Also, is your video card a dedicated graphics card? Or is it an integrated card?

yes I know the hard drive has little to do with it, but i figured for some people...

its integrated card. I shouldnt have had superfetch on to begin with. Also, GameBooster claims to suspend and terminate all processes not relevant to the game it is 'boosting', so I should not have a decaying fps issue when launched through this.

Well, to those following this, I did find a solution eventually. Re-install the game. Not a perfect solution, but I get something that oscillates near 45 fps. Lowering the quality bumps it up to 60. Possible that my data got corrupted by random charged particles from the cosmos.