It does sound like you have a heat issue. If you find an accumulation of dust inside the case purchase some canned air and blow it out. Pay particular attention to the heat sink and fan assembly on the CPU and the intake vent/s.
You have mismatched RAM modules, this will keep it from running in dual channel which helps reduce the bottleneck between the CPU and the RAM.
When was the last time that you defragged the hdd and disk cleanup?
You would benefit from deleting your temp. files, I've included instructions below.
Please download TFC
by Old Timer and save it to your desktop.alternate download link
- Save any unsaved work. (TFC will close ALL open programs including your browser!)
- Double-click on TFC.exe to run it. (If you are using Vista, right-click on the file and choose "Run As Administrator".)
- Click the Start button to begin the cleaning process and let it run uninterrupted to completion.
- Important! If TFC prompts you to reboot, please do so immediately. If not prompted, manually reboot the machine anyway to ensure a complete clean.
When was the last time that you scanned for viruses or malware?
If you defrag the hdd and use the disk clean up you won't gain that much by using ccleaner.
Edit: Is this a custom build? If it is you may need to reapply the thermal compound between the CPU and the heat sink.
Edited by dc3, 11 December 2010 - 12:22 PM.