Computer running slower than usual

I've been having some problems with my computer running slower than usual although I haven't installed anything recently in the start-up queue. I ran the usual malware scans and the computer seems to come back to life for a short time then it gets slower again. This morning I turned off my computer because I was doing some work around it, but I did not disturb it or unplug anything and when I turned on the computer all of my icons disappear from my desktop and there was a message saying Windows group policy was not running. I couldn't even turn off the computer from the power icon, I had to turn off the computer from the physical power button on the computer.

I send my scan logs in for review but they were clean. Any ideas what could be causing this problem?

I have an HP m90n computer running Windows 8.1 64bit.

 

Remove any unneeded programs. Check to see if there are any programs you can keep from starting automatically on the startup tab when you run MSCONFIG. Make sure you have created a restore point before you modify anything though. If you need further instructions, just ask.

 

TimW & dr.moriarty - Both are good advice. I use winpatrol at startup for monitoring changes. I also run Startup cpl and Autoruns fairly regular. These along with process explorer can show alot of what's going on. I would go a step futher and recommend everyone should run these regularly before there is a problem so as to be familiar with what normally should be there.

 

Thanks all for your suggestions. I've cleaned up the start-up list but the problem is the same. I ran sfc /scannow in both regular and safe mode and it says there are some system files that are corrupt that it cannot repair. What is the best way to fix these corrupt files without having to re-install Windows?

 

Thanks for the info, I am considering this option