Sorry the drive space solutuion didn't help.
The next logical issue is something else is running in the background and causing the problem
What are you using for Firewall, anti-virus, anti-spyware, etc.?
A quick test would be to disconnect your system from the internet, turn off all of those programs, and see if it's any better.
You may also have stuff running in the background you don't need.
A handy program I use to help to keep unnecessary stuff from loading is Advanced Windows Care.
This program does a lot of other "optimization" stuff, but it includes a check of all the programs set to run at start up. It includes a feature to let you look the program up on line to find out exactly what it is and what it does, so you can make an informed decision on if it should or shouldn't run.
The third possibility is that some other program is running a scheduled task that sucks up resources or creates a conflict.
If you want to monitor the temperatures, you might want to run a program to keep track of that.
My motherboard came with a program called "Windbond hardware doctor". It continuously monitors, temperature, voltage, fan speed, etc. and is configured to alarm if anything exceeds a threshold.
Not all motherboards have the hardware to support this particular program, but it might be worthwhile to see if you can get one of the various software packages to work on your system. Do a google on "motherboard monitoring software" to get a bunch of candidates.