Thanks for the answers!
Yes...there is a much better product suitable for your situation. Please consider using Microsoft Security Essentials. It's fully automated and it's default installation settings are just fine.
Your issue however is caused by a combination of errors...the heavy usage of resources from the Symantec product combined with a conflict with the native Windows Defender is also causing system instability.
By default, Windows Defender is turned on in Windows 7. Symantec cares nothing at all about writing their products to accommodate other security products one may have on board. As such, upon installation, the conflicts begin. Microsoft Security Essentials is written with other security products in mind such that upon installation, the Windows Defender is turned off to avoid conflicts and wasted resources.
First, you must use the Symantec removal tool to untangle it's strangle hold on your system. That product is more difficult to remove than some of the rootkit infections I have encountered over the years.
You can download the removal tool Here...
follow the instructions on that page.
When you finish, please download and install the Microsoft Security Essentials from Here...
When the installation completes, you can feel confident that your system is protected automatically. That software will download updates automatically and will schedule automatic scans for you.
Before you go much further, you should also uninstall the Crawler Toolbar with Web Security Guard
. Otherwise, you may be interrupted by alerts from the Microsoft Security Essentials real time malware protection feature.
Next, I need to point out the system errors that show in the log:
2011/01/20 04:59:44 PM, Error: Tcpip  - The system detected an address conflict for IP address 220.127.116.11 with the system having network hardware address 02-50-F3-00-00-00. Network operations on this system may be disrupted as a result.
2011/01/20 02:22:34 PM, Error: Disk  - The driver detected a controller error on \Device\Harddisk1\DR1.
2011/01/19 01:22:30 PM, Error: Tcpip  - The system detected an address conflict for IP address 18.104.22.168 with the system having network hardware address 02-50-F3-00-00-00. Network operations on this system may be disrupted as a result.
...the Tcpip error indicates that another computer on the network may be using the same IP address. Each system should have a unique address of it's own. That particular error is something your IT folks should certainly be able to rectify.
The Disk error should be resolved by following the instructions in This Microsoft Article
Post back when you've gone over all of these instructions and let us know how the system is behaving at this point. There is much more to do. Good luck!