Huge problems with digital signatures/corrupted or damaged files etc. Help! :)

Hello.

Recently I have had some big issues with my computer. The computer has gotten slow (especially in games and heavy softwares) and it has huge problems updating computer softwares and installing them. In many online games, my fps often drop under 10. Can outdated drivers cause this? I have tried to update my drivers (I have Intel Core I5 2500k and ATI HD Radeon 5700), but then the screen got all messed up so I had to do system restore.

I also feel like I have lost some administrational rights, since it often occur that I cant open folders "because I dont have the admin rights" and often have to manually open programs as an administrator.

When I install new programs, I often get error saying that the digital signatures could not be verified or that it is something wrong with the "integrity". I cant use the windows update, I get the 800B0001 error. I have tried running Microsoft FixIt, but then I also get an error saying that it could not be installed because there was something wrong with the intergrity.

I have scanned with antiviruses several times (AVG, Avast, Malwarebytes and Spybot S&D). I had some kind of PUP.Optional "adware" (I dont think its classified as adware). I have deleted it and all the files and registry keys with it. It seems that some of it may be left since I get redirected to "www.my-online-search.com" when I open new tabs in firefox.

I have tried running SFC /SCANNOW, where it found several damaged files but could not repair them. I have tried to check out the log file, but I don't have the rights to open it. It seems like "TrustedInstaller.exe" is preventing me from opening it. I have also runned CHKDSK.

I have cleaned the whole computer, runned defragmentation and deleted 100gb of files and softwares. I have also done everything to increase performance (even windows 98 design, removed wallpaper and almost no startup programs). Is there any way to simply repair windows? I dont have the CD, it was already installed when I got the computer. I dont want to spend up to 100$ to just open a chat with microsoft, lol.

Some help would make me really happy

Thanks!

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