As to registry cleaning...
Many of us on the forums actually do not recommend automated optimization tools for Windows 7. Windows 7 does a much better job of handling its own optimization than its predecessors did. We especially do not recommend registry cleaning as an "optimization" step because automated registry cleaning causes more harm to the registry than it actually repairs.
In the future, if you need help optimizing Windows 7, please post a thread in Performance & Maintenance - Windows 7 Forums
or follow the tutorial enclosed in that forum to Optimize Windows 7
How old is the system? Is it a laptop? Have you tried blowing the dust out of the system?
- To remove dust, follow the following general procedure. If you have a desktop bought from Dell, HP, Sony, Lenovo, etc. make sure removing the desktop casing will not void your warranty first. Call the company if you are still under warranty and ask if it is okay to remove the casing and blow dust out. The procedure described is fine for laptops; just make sure no stickers are on panels saying if you remove the panel it will void the warranty.
- Shut down and turn off your computer.
- Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
- Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
- Remove the casing for a desktop, or remove any screwed on panels and disc drives for laptops.
- Blow out the dust inside by using a can of compressed air or a low pressure compressor. You will want to put the computer on a desk or table so you can maintain the can in an upright position if using a can of air. Blow into all crevices on the motherboard, heat sinks, cards, modules, etc. for a desktop. Blow into vents, opened panels, disc drive areas, USB ports, and the keyboard if it is a laptop. You may also want to blow inside the disc drive by replacing the drive to the laptop, starting the computer, opening the drive, and then turning off the computer and removing all power as described above including the 30 second power button step. For a desktop, you may also want to blow inside the disc drive by starting the computer, opening the drive, and then turning off the computer and removing all power as described above including the 30 second power button step.
- Replace casing for the desktop. Replace panels and disc drive (if you have not already done so) for the laptop.
- Plug power supplies in. AC adapter for the desktop. Battery and then AC Adapter for the laptop.
- Start the computer and see if performance is better.
- Monitor the temperatures and post back the temperatures during freezing. Download and install SpeedFan 4.45 to check temperatures during freezes and also during idle. Post back the temperatures for each case.
- You may also try to Troubleshoot Application Conflicts by Performing a Clean Startup and see if it might be a program or service causing the freezing.
- Run SFC /SCANNOW Command - System File Checker up to three times to fix all errors. Post back if it continues to show errors after a fourth run or if the first run comes back with no integrity violations.