Performing Maintenance Help

So, my computer is around 3 years old, I've always took good care of it, but recently, it suddenly became significantly slower, it is not noticeable when surfing the net or writing up essays with word/powerpoint, but there is a significant FPS decrease when playing games, assassins creed and mass effect use to run on a very stable 58-61 fps, but recently I'm experiencing drops to around 40 fps, and spikes occur very often

My computer's specs
-Intel core i7 950
-12 gb ram
-Nvidia geforce 450
-1 TB hard disk with another 1TB added a year ago
-System is windows 7 home premium 64bit

Maintenance I perform regularly
-CCleaner
-Defragmentation
-disk cleanup
-SFC
-Full scan with malwarebyte and kaspersky
-Deleting %temp% files
-Deleting cookies/temp internet files/cache
-Not often, but my router used to screw up and i flushed my dns several times

So I currently have no idea whats wrong with my computer, Im pretty sure its not a malware/virus as I'm a very conservative and safe user if I say so myself, sometimes I go on virustotal to check files that I suspect

Im starting to think that there are some configuration errors/resource allocation problem/system corruption that is bugging my computer but I have no idea how to find them or solve them, are there other programs that can scan for non-malware related errors that can help optimize my computer or simply identify my problem?

Any suggestions to fix my computer would be welcome

bobafetthotmail said:

Taking a rough guess, it's possible that you have unnecessary background processes. A lot of things you install love to add themselves to startup as it make the application load faster.
Try this tutorial, method three.
And disable most of the programs you can recognize (google the name to find what it is if not clear).

Followed it and there arent much in there, just some adobe updaters, java, itunes, quicktime etc. I disabled some, but it doesn't seem to help or affect anything

I keep thinking there is something wrong with my system files, is there any way to check them apart from SFC or a better reigstry scanner than ccleaner?

Hello Brink, recently my computer has gotten really slow, I've done everything I could find and think of (disk cleanup, defrag, sfc, ccleaner, malwarebyte scanning) except for a repair install but in the end it doesn't seem to solve my problem.

I've never messed with the system before, so Im actually quite scared and I was hoping if you could clear up some misconception and worries

-Do you think a repair install would help at all with my speed issues?

-Does repair install overwrites your current system or does it installs a new one? do I have to delete the old one then?

-The tutorial mentioned that I have to re-enter my product key activate windows 7, (sorry im noob) I have the Disk and the Key but aren't those one-time only (I have no idea)? do I have to deactivate window 7 before hand? would a situation happen that my key becomes unusable?

-Repair install preserves my data right? but can you tell me in what way? does my desktop still stay the same? are the registry changed? will my programfiles or user/appdata be affected? and I know some programs like .net framework installs itself to the c:/windows directory, are those affected? what exactly does repair install change?

Thanks in advance