Why is my pc slow and freezing

Often a hard drive that is very full or is highly fragmented will react this way.

I would recommend first making a backup of anything important. Then delete anything that you really don't need. Next clean out the old log and cache files as they too often are not needed any more. The last step here is defrag the drive using the tools option by right clicking on the drive and going to Properties at the bottom, then the Tools tab. If the drive fails it's time for a new drive.